Finally, an update!
New sunroof assembly arrived today from Mr. Hardcor3... much appreciated dude
Have started this evening my removing the headlining. All in all not a difficult task (why the haynes manual says seek professional assistance I don't know!). However, where the sunroof had been leaking there was a lot of condensation and the lining was a little damp. I've left it off to dry, so will resume tomorrow evening. For now, I'm just driving around in a car with wires dangling from where the interior light should be. Shocking!
Some good sound proofing on the roof mind
Will try and do a step by step with photos of the sunroof swap. Wasn't much point in the headlining, is fairly straightforward.