I also went to Park Lane and test drove a Six over a year ago simply because they are only about 10 miles down the road from me

. I almost bought a Silver E6 from them but I really wanted an Icecelle example and I was promised that someone was p/xing an immaculate one for a new R34 GTR with a week or two. That stretched into a month and then two. After ringing many times and promised many phone calls back that never happened it became apparent they weren't really interested in a sale so they never got my business.
The prices may be expensive on the site but you can knock them down a lot, I got almost £2k off that silver E6 which brought it in line most other places. Yep they do get some tasty stock including recently a 964 RS, they had 3 R34 GTR's when I was there (when they were virtually new). By the way there was black WRX Type R that must have been siting there year before being sold, it gives you an idea that they aren't too worried about shifting stock.
Park Lane are the only independant SVA test station in the country so importing is easy for them, in fact I was told Park Lane imported and SVAed all the Ralliart Evo 6's on their behalf. As for servicing, well they will do the oil change but take the car to Mill Lane Mitsubishi for the AYC fluid swap, seems a bit pointless taking your car to them in the first place really.
All in all much like DaveG says really except they are not as professional as they first seem.