I don't think it's too far from Basingstoke but Camtune in Godalming might be worth a look. Usually a Porsche specialist but at the moment they seem to be doing a lot of Mercedes'
Try Roy at Autobarn on the A30 towards Hook. Based at Priory farm. There a few of us from the TT forum who take our cars there. He does a good job at a good price. His number is 07787315568.