The travel Gods must be happy with me because I received an email today from Avis Customer Service informing me that they are refunding my £900+.
It is a bit weird though...
Just as a recap (for those not remembering the start of the thread)... I was informed by Avis I had a 15hr grace period to pick up a rental. Well, it appears that the 15hr grace period does exist. They will hold a booking for 15hrs after the original booked pick up time before releasing the car back to the pool. What they failed to tell me was that although they will hold the car they don't hold the rate. The rate can change!
It would have been nice to have been told that my rate may significantly change if I pick up the car late.
Never mind... lesson learned... for both me and hopefully Avis!