Yes Avis does have shady business practices in some locations. I have rented from Avis at LHR three times in the past few months. First return "printer isn't working, you'll get an emailed receipt" - charged $200 for gas in car that I had filled to the brim a mile from the return location. They ignore my complaints and Amex fix the issue. Exactly the same thing happens a couple of months later and again Amex fixes the issue after a dispute (luckily I had kept gas receipts in both cases).

Last week I arrive to pick up my car and my name is not on the preferred screen. Wait 15 minutes to talk to an agent in the shack and he says there's an issue with the rate and I need to go to the main office. Go to the main office, wait another 10-15 minutes and then get set up with a car. Car has damage on all four corners, all four wheels are dinged, front and rear bumpers are scratched - hardly a "premium" vehicle, but I'm in a hurry to leave now. Turn the car in 4 days later, again no paper receipt because "the printer is broken". Get the email an hour later and I've been charged $510 for my $178 rental - receipt shows a completely different rate to what I reserved. Currently trying to resolve with Avis before I escalate to Amex, but their response so far is that I made a last minute change to the reservation. No I didn't - your agent didn't know how to process my reservation.

I'd look elsewhere, but all the car rental agencies seem to be just as bad and dishonest