I get my part numbers from the Genuine RR Parts Manual - wasn't cheap but worth every penny - and it sits alongside the equivalent Workshop Manual publication.
Two large volumes that stop my desk drifting away and also that I can carry about and make notes in.
They are available for a lend Joss if ya needs them as you're only about ten minutes from my place.
That would be awesome. Thank you Fergie, I'll keep that in mind. It's always good to have other member local for advice and help