Would recommend CJ Saab as in sgould's post above. Clive is ex-head Reading Saab spannerman and very good, though busy and sometimes hard to get hold of.
Though it's a measure of the regard in which I hold Saabtech, formerly of Stevenage now of Welwyn, that I go there from Oxford. I'd talk to them about anything like this - massive expertise, and very honest and price-conscious with it.