I'm probably mis-remembering discussions of this:
There are various allowances for helping fellow riders and other worthy reasons. Many AUKs tend to be relaxed about intermediate time limits.
there is no hope of me finding a reference - I find all the ACP/LRM stuff most opaque, sorry!
Of course there is bound to be some grey areas in such rules. There will be events where if you submit your receipts with a convincing tale of woe, you'll be ok - but don't submit them with a note saying
"MattC said this would be alright."
I think if I was riding a UK600 and looking at booking accomodation, I would try sounding out the organiser on his views. Unless I didn't give a monkey's about the points.
There are certainly many of us in AUK who have had long brevets validated despite finishing (or controlling) out of time. In the UK and abroad. C'est la vie!