Cadbury's chock despite being available in Canada is so much better from the UK...
The Canadian stuff is made by the USA's Hershey at their Canadian plant & is utter shite in comparison.
So any real Cadbury product...
Also real MARS BARS

OMG I'd kill for one right now.
Biscuit wise, again cadbury's choc covered bic's such as fingers or digestives...
Hob-Nobs
Ginger nuts (by McVitties) too.
Tea, I don't drink the stuff but hear that PG Tips is the dogs bollox.
Real Branston pickle (again, it's dif from the stuff made in canada) as are pickled Onions...
Got to have some Eccles cakes if they have any...
Treacle tarts too...
Ohh, the local place here does some nice 'other stuff' too...
Birds custard,
Cadburys drinking choc,
Heinz baked beans (ohh so dif from the US & Canadian)....
Tate & Lyles "Golden Syrup"

Tizer
Lucazade
Ribena
The shop here is a rip off tho'

It's a tourist trap & not intended for real UK peeps
When I go to DC I visit the embassy & stock up

Much nicer & a lot cheaper (Duty free too).