I can't help with the part number, but I would if I were you just pop along to a auto gearbox place so they can test drive the car, as you could be chasing problems all day, could save buying a few parts that don't cure it, they don't normally charge anything for this, can't recommend anyone in Ipswich, but JR Danes in Norwich is excellent, 01603 407372, the last mondy auto box they fixed for me had been condemed by 2 other experts needs full rebuild etc,(only done 12,000 miles since rebuild), a £38 lecky shifter later working perfect.
tabetha