Just sold the old Audi onto WBAC for £700 more than the dealer offered in PX. Pretty happy with that - it'll pay for some of those extras I added!
Personally I thought that WBAC's service was very courteous and professional, not sure where they get their bad reputation from. The chap I dealt with was polite and realistic about the damage to the vehicle, took £200 off the online valuation for some scuffs on the alloys, a scuff on the front bumper and some light paintwork damage and denting where my side sill had a disagreement with a large rock. All in all quite fair.
He did say they get a lot of chancers trying to palm off clocked cars and undeclared write-offs on them, and they get irate when they aren't given anywhere near the online valuation price, maybe it's these guys giving all the bad reviews!