thanks for the help guys. I do feel I press the brake all the way, the jolt is forward motion by what I assume is the selecting of the gear. It pulls away smoothly, it's just that selection process. The car has 137K on it, it seems genuine, but I only have history to 122K, it's having a cambelt this coming week. As some stage it's had an offside impact and the driver door has very slight evidence of repair (evidence of orange peel, door shut line not consistent, but not touching anywhere. sadly it's had a set of after market wheel put on it at some point, they could be a lot worse, and to the untrained eye you might mistake them for OEM (16" OZ racing 6 spokes), but they need to go. As for the seat, i'm 6ft 7" and broad shouldered. I refuse to compromise my driving position by leaning the seat back, so i'll get another seat on eBay and experiment with cutting and shutting.
I'll get pictures up this eve. Thanks again.