£50 ??!!! Just after posting the query, I called in at Mike Duncan's and he had one - said it was from a Landrover of some sort - and it cost me just under £100 for the full thing including two new keys !!!
Then it took me about 3.5 hours all in to fit the bloomin' thing ! And I had fun wiring it up because two out of 4 wires were different colours to the originals. Still, got it all on and it works a treat now. The starter motor definitely spins faster with the new switch and does not sit there going click click like it did before.
thanks for the info - next time I'll get an MGB one !
Matthew