Depends what market you are in
Cleveland Street Car Sales in Birkenhead are good, guy is pretty conscientious.
Frankby Motors and Irby Motors are ok, never heard any complaints, relative buys from Irby.
I was impressed with Sovereign Cars recently (very nearly bought a car), Seabank Road, New Brighton. You can't negotiate much on price but the prices are very realistic for trade.
Stoneacre New Brighton are a good company (much to my surprise), screen price a bit high but you can negotiate, sales guys can be a bit sales-talky (sit and bear it) but after sales is good and their servicing/repair/MOT plans are really good. Part of quite a big company.
My current recommend for the higher price bracket although a distance away is Wilmslow Car Sales, guy is really 100% keen to uphold his reputation, people buy cars blind off him from all over the place, even Ireland. Prices are pretty good for trade, relative bought one recently.