Things are looking up today, firstly I tried ErnieA's suggestion with a wooden block and mallet, but no luck with that one. Next I pulled the right side tupper ware and the bit of frame from in front of the crank case cover, 10 srews latter and the ccc dropped away with no problem. I located the sprag assembly, trod the gearbox up to top gear and emptied about a can and a half of Roco Electra clean solvent aerosol into the 3 holes around the sprag by turning the engine over by pushing the rear wheel round with my left foot and with a 200w lamp trained on the sprag holes, also did a bit of tapping on the side of the sprag assembly with a wooden dowel and mallet (but pretty sure that didn't do much).
Anyway the solvent did the job, with the gearbox back in neutral, one hand on the start button and the other on the kill switch (still got the ccc pulled remember) and the starters spinning the engine over :dance: .
So having contaminated the engine oil with solvent, although most seems to have run out of the open ccc and I guess some will evaporate, before running the engine the oil will be changed for Shell Rotella diesel oil for its enhanced cleaning properties and hopefully that will help keep the sprag clean and stop it hanging up in the future.
Thanks again guys for the help and support :bmw: ..