To cut a very long story short - wrong shock supplied ( was sold a 2009 one).
Sent my one for a re-furbishment. £173 later and no improvement.
Was costing too much to keep having it put in/ taken out, so I thought I should learn to do it myself.
First attempt 3 hours, now down to 30 minutes.

MacGyver - eat your heart out.
Anyway, the shock was then found to have leaked it's gas (apparently never been seen before and must have happened during manufacture), well whatever. The chaps then did major surgery and drilled and welded a Schrader valve to re-gas with nitrogen. They also fitted an Ohlins spring.

All now re-fitted. Just waiting for a dry day to give it a fair test.

