It also assumes he'll be able to talk at all while eating Hagrid's cooking, but Hagrid is blissfully unaware of this hazard.

Bruce and Hagrid will traverse the tube system back to Little Whinging, then! (The less spoken of this activity, frankly, the better.)

Upon arrival, Hagrid will evict a variety of newly purchased packages from his coat, to pile into Bruce's new school trunk. It may at this point become clear to Bruce that, even though each of those items individually definitely could have fit into Hagrid's immense pockets, and so it didn't look odd when he was putting them away shop by shop, they probably shouldn't all have.

"Are your pockets bigger on the inside?" What else from Doctor Who is real?

Hagrid peers in surprise between the pile of packages and his coat. "Guess so?"

"Was it not like that when you bought it??"

"Nah." Hagrid shrugs unconcernedly. "That sorta thing happens sometimes 'round lots of magic, and Hogwarts is one of the most magic places there is."

"Wow. Is it usually good things like extra pockets and not bad things like stuff catching fire?"

"Eh... " Thoughtful beard scratch. "Yeah, think so? Least at Hogwarts. S'pose I wouldn't bet things don' ever catch fire outta nowhere at Durmstrang."

"What's Durmstrang? Another magic school?" Is it where they send you if you set too many things on fire.

"One of the big ones on the continent, yeah. Terrible place, just terrible, Darker than anything. Least the Slytherins at Hogwarts gotta answer to Dumbledore."

"That sounds bad for magic kids who live on the continent."

Shrug. "'Course Hogwarts is the best there is. Think Beauxbatons is all right, though, 'sides bein' French an' all."

"I'm glad I get to go to Hogwarts. . . . I guess you probably need to go back there soon." The Dursleys seem to have decided that being on the other end of the house from Hagrid is the better part of valor, but he's blocking the stairs and it can't last forever. He got enough time to let Curie out the window, so she'll be alright at least. 

Hagrid is not thrilled to have to leave Bruce here either, but this is not false. He very carefully pats Bruce on the shoulder, as bracingly as it is possible to do without knocking him over, and takes his leave with a reasonably cheerful "See yeh soon!"

"See you soon."

The next month is one of the least directly unpleasant and the most anxiety-ridden ones he can remember. Dudley makes himself easier to avoid than usual; his friends follow his lead. Uncle Vernon and Aunt Petunia argue about whether having him out of the house for nine months is worth the price of letting him "go to freak school to learn to be even more of a freak," but the trunk under his bed stays unmolested.

Curie proves remarkably good at avoiding their notice while sneaking in and out of the house; it helps that she's nocturnal, unlike what the library books say. Maybe magic post owls are bred for stealth and night flying.

Bruce does his chores and avoids notice and reads his textbooks in bed when everyone else is asleep, with a blanket shoved against the crack under his door so nobody can tell the light is on. September approaches the present like a fog bank approaching a boat, a blank wall of inevitable unpredictability.

Uncle Vernon does, ultimately, drive Bruce to King's Cross, with his ticket and his trunk and "that damn owl who had better not come back here" in her cage. 

"Well, there you are, boy," he says. "Platform nine--platform ten. Your platform should be somewhere in the middle, but they don't seem to have built it yet, do they? Have a good term." And he leaves Bruce and his eye-catching array of cargo staring at the barrier.

Alright, Bruce thinks. Nobody would have done all that stuff with Diagon Alley just for a prank, so there's got to be a platform here somewhere and he's just forgotten the directions for it. Maybe it's like Diagon Alley, where you've got to tap a specific bit of wall. He pulls his trunk with Curie's cage on it up against the barrier between the platforms and starts doing what he hopes looks like idly drumming his fingers on the bricks.

Good (?) news: This is not a wall.

It is, on contact, the distinct absence of a wall. The precise opposite of a wall, perhaps.

!

Does that mean he can just grab his trunk and shut his eyes and--walk a couple steps that way?

Shutting his eyes will help a lot! 

At once, the sounds around him change. King's Cross proper, on a Sunday morning, had been full of the ambient noise of modern folk about their business: the beeping of someone or another's pager, dozens of trains arriving and leaving, the periodic tinny crackle of announcements over the loudspeaker. Platform Nine and Three-Quarters, by sharp contrast, is characterized by the shouting of a great many excited children contained in a relatively small space, the hooting and fluttering of dozens of caged owls, and, of course, the singular and unfamiliar hum, overlaying it all, of a train that is not quite just a train.

Woooow!

He's gonna get on the train!

Nope, he's going to stand on the bottommost step leading up to one of the carriages, hauling on his trunk and failing to get it all the way off the ground.

In the moderate distance, a clamor rises just slightly above the ambient shuffle, as a boy with bright red hair arrives through the wall with his trunk on a cart, moving at a headlong sprint with two cackling probable-brothers not far behind. The lot of them very nearly end up in a pile on the ground. Their voices, bright and gleeful, are indistinctly audible in bits and pieces:

" - honestly, you call yoursel - "
" - ickle Ronniekins - "
" - a Hogwarts toilet seat -"

The younger boy heads for a carriage a little farther forward and the twins move towards the one Bruce is trying to get in.

Bruce tries harder to stop blocking the stairs, loses his grip on the handrail and falls out on top of the trunk.

"Sorry, sorry--I'll get out of the way--"

"Get out of the way, he says, and immediately gets more in the way," snorts a twin, and the other agrees, brightly, "Firsties! Gotta love 'em! You need a hand there mate?"

"Um. Yes please?"

They each grab one end and heave it onto the train with the ease of long practice and teenage muscles.

"Oof, mate, what've you got in here, a rock collection?"

"Books," he says guiltily.