Well, it went in, I ended up ignoring your advice, Tim, about centring the plate as I have a 1/4" extension bar which fitted just so with an 11mm socket attached and I felt confident/Lazy. The only problem was I broke the tabs on the clutch release bearing and had to wire it on, all seems to work fine so I'm very pleased with myself. Took about 7 and a half hours. Found a top tip of my own during the reconstruction, used an old expansion vessel and hose to refill the gearbox, popped the tube in the side hole,wedged the vessel twixt battery and rad and put the required amount of oil in, an hour later it was all in the gearbox.
Thanks again