The typical causes of pulling to one side:
1. Tyre inflation differences
2. Spring (3.2 - torsion bar weak or broken)
3. Mismatched tyres
4. Wheel alignment (combination ot toe and cambers)
5. Wheel bearings worn or defective
6. Anti-roll bar and/or links defective
7. Incorrect castor / disparity on front castor angles
The links below give Midlands shops that can do the work, PCT (Autobahn), Porsche OPC Solihull, Jeff Fowkes. There is Ramus in the West Midlands, Zentrum Notts.
http://www.porscheclubgbforum.com/fb.asp?m=172520&key=alignment
http://www.porscheclubgbforum.com/fb.asp?m=181232&key=alignment
You can save yourself a great deal of money by making sure the rear camber and toe-eccentric adjusters are nice and free. This is a usual source of fun and £££'s in time to free-up if the alignment shop has to do it.
Typical high street charges for a check and/or report are £15 to £30.00. The Porsche specialists charge more because of the knowledge they bring. Adjustments charging can range from a rate per hour or £10 to £20.00 per adjustment. Typically for a 15 to 20 year old, alignment shops may set the worst expectation and may say all day! However, the report may show nothing requires changing. Corner weight balancing is more specialist, have alook at the link given by Richard B, forgive its age, but does give some clues as to cost/availability:
http://www.porscheclubgbforum.com/fb.asp?m=5347&key=corner%2Cweight%2Crecommend
(also check how old the dampers are, if they are the originals changing them certainly will smarten handling up, as well as the rear radius arm bushes which deform over time)
Hope this helps a little.
