Well all done (sort of). Can't believe how easy it was (apart from a bit of wrist/knuckle scraping to get to the clutch switch.) As you said Mark, it's SO much easier to just put steering wheel in highest position. Think I was done and back together within 15 mins.
Slight problem is the second hand clutch switch I had been sent had one retaining lug broken off, so wouldn't stay secured in its mounting place. Instead I decided to just bridge the connections on the plug that goes to the clutch switch for now... and it works a treat.
The C/C still deativates when clutch is depressed, okay is not as instant as it probably is with it fitted, but the revs come up momentarily and it's off then.
I will get another switch eventually I guess, but it's not worth paying £25 quid from Vauxhall TBH, I'll keep my eye out for another second hand item.