Iv'e just taken delivery of a MEX Roger Waters Artist which I got out of its box only last night. Haven't had much time to do anything with it yet but first impressions are good.
I ordered the bass from Dawson's and I found all the guys I dealt with there to be knowledgable and extremely helpful. A real delight to do business with.
I agree with all the above advice, try lot's of different basses because quality does vary throughout. If you find one that you really love in a shop, haggle. My local shop had the RW up for £767 and when I walked out the door told me I could have it for £583!!!! Got it from Dawsons for £40 less than that again.
On a similar note, I bought a Squier 50th Anni Precision from here a little while ago for £100 and I absolutely love it. It's just a very personal thing. Cheers CD_ David.
Good luck with your search.
LC