Thanks Ian. All I can think is that I must have 'pinched' the wiring when lowering the subframe. I think I will raise this again and retrace my steps. Thank you for your time..
Problem sorted! Thank you all for your advise and suggestions, in particular 'Ian J Hartley' and 'Galactic Greyhound'. I traced the problem to a faulty neutral switch at the back of the gearbox. A second hand replacement from Motorworks has everything working ok.
I finally learnt how to use my multimeter and test lead to trace the problem, rather than spend a fortune on replacing parts at random!
I wouldn't have been able to do this without your help....