JTD is oversprung and underdamped which makes for a choppy ride at low speeds and on uneven surfaces. Presumably HGT springs are stiffer and 1.8 dampers won't be brilliant for the increased weight and performance. Probably better to fit the springs (not so hard) from the older TD with decent dampers such as Konis which would give a much better ride. Just my 2ps worth. Better still get rid of the car and buy something we a better ride.