When I bought my RRS the alloys needed refurbing, so I've been around a couple of places, all seem to offer the same service & "guarantee" but prices (for all 4 wheels) vary from £240 to £456!
Any good or recommend suppliers? Any potential problems?

Yes - wait until you need four new tyres, buy them from an on-line supplier (Camskill, mytyres etc) and have the tyres fitted by the refurbisher when they do the wheels. Saves £20 per wheel on fitting and balancing.

A friend of mine had two sets of wheels from a Jag and TVR refurbed by Autowiz in Welwyn Garden City and was pretty happy. At the other end of the price scale is Lepsons in Kent; top job but high prices (had my RRS wheels done there). Lepsons will match the factory paint finish which was silver sparkle in my case.

For a personal service ring Chris at Excel Wheels, he's local and famed throughout the Porsche community for quality. 2008 MY Java Black TDV8 HSE