I'm a seller rather than a dealer and thought you'd like to know the pitfalls with Blackbushe.
The car I sold in the last 2 months had it's reversing sensors disconnected (water damage) and the aircon was so old it had fallen off the it's engine mounts. The turbo seals had gone and was doing half a litre of oil every 500 miles. Despite this WBAC gave me cash and I was grateful.
Within a week some dealer in Surrey had it on sale with sensors and aircon working (unlikely)
What was of note was that the car should have gone to the BCA site 20 miles away as it was over the 5 year limit for Blackbushe but they sent it to Blackbushe anyway. So avoid anything over the stated BCA limit there.
Disclaimer: My day job is in consumer protection so I am not surprised about b2b deals.