I am aware that the Basingstoke market area for BMW is a bit odd, most major manufacturers are represented in central Basingstoke bar BMW who are 5-6 miles away in sleepy Odiham in a high street location with a very small showroom and nothing like the 'gin' palace you would expect. Harwoods are getting big now form starting out as just a LR dealer they now encompass quite a few prestige dealers and I wonder if the purchase of Hampshire Cars is there way of trying to get the full BMW franchise in central Basingstoke?
They only thing I would say is that there Audi dealer in Porstmouth is shocking to deal with and have heard of friends having issues with their other Audi site in Five Oaks.
I'm amazed that you kept going back to them. If I had had to go back more than 3 times I would be finding somewhere else for sure. As far as other dealers to try, don't bother going south to Scotthall in Chanders Ford, Wood in Odiham worth a shot but have had no dealings with them, sisters current + previous cars came from them both with great service if a bit on the pricey side

Fingers and legs crossed you don't need to see any of them
