Ian Jelf wrote in message ...
Thanks for all the advice, everyone. Just back!

I used West Ruislip in the end, which still had some spaces left around
8.00am. Not many but a few. I was impressed that there was an
attendant selling the day tickets, too. No need for the pocketful of
coins I was lugging around, after all!

(Incidentally I must e-mail LUL; the Station Assistant at West Ruislip
was one of the friendliest people I've ever encountered!)

Thanks again to all who made suggestions for the advice.

There was an SA at West Ruislip? Rare indeed. I never saw a member of
station staff in the two months I was based there.