[largeformat] 4x5 B&W in London

[LNPhoto]

My wife's lifelong dream is to go to England.

We've booked the Queen Mary II to get there, which means we'll only 
have a 5-6 days to play in London.

I want to do some street shooting with my 8x10 Deardorf, but will 
settle for my trusty 4x5 Crown Graphic and some B&W film.

Am I better off processing the film in London before I meet the 
security trolls at Heathrow?

If so, who in London would be able to process it?   I'd prefer to shoot 
TMX  but could shoot a chomogenic film if I had to, but I would think 
it would be easier to find a lab or old photographer that could 
tank/jobo process B&W  easier than finding a lab that has a C41 
processor that can handle 4x5.

Any advice about any part of this vacation would be greatly 
appreciated.......

......well advice other than seeking professional psychological help, 
we've long established my certifiability