Thanks to both of you for the advice.

I'll print out this thread and decide while waiting in line at passport
control.

Incidentally - having posted here on and off for several years now (I
believe my first post, in 2006, was complaining about inconvenient - to
me - scheduled engineering work at Heathrow T123) - I wouldn't mind
meeting some members of the group while I'm in London. (Actually, I've
already met one, but that was in New York.) Sent me an email if you'd
like to meet up - although my Internet access will be spotty at best in
London (anybody have any suggestions for free or inexpensive wi-fi in or
near Hendon?), so it would be best to catch me by 5pm New York time
(10pm London time) on Wednesday. I'm in town until 18 November.
--
David of Broadway
New York, NY, USA