Thanks again for the responses.
Ive got this week off work to try and get it finished.
OK so today I started out by digging out the stock chip and trying that instead. Again started up fine. The idle wasn't hunting as much as with the other chip - was not rock steady though. I just ran it for a minute and switched off. I won't bother again until I'm going to drive it. I think the stock chip is the safest option for the time being. Once I'm driving it around I can try the other chip again.
Then tidied the garage up - god there was a lot of dust!
While I'd been eating breakfast I'd remembered that I still hadn't connected the clutch thingy (slave cylinder?). It's held on by 2 nuts, but to get them onto the studs you have to compress the hydraulic clutch rod. You have to do this lying on your back under the car, with your arms stretched out up onto the side of the engine/gearbox. It's stiff. Very stiff. After half an hour of grunting and swearing under the car I gave up.
Then I went onto the rear bodywork - this is the hole I need to fill
Bit of bending, shaping, hammering and got to this stage
Screwed it in place to help get the positioning right
Bit more fettling and I've ended up this this - should be OK
Once that was done I returned to the clutch slave cylinder. Spent an hour making a special tool to let me wind it into place using a threaded bar. Spent another hour trying to make that work.
Had tea
Went out again. Special tool not working. Tried to force it in again - just not happening. Eventually I got a crowbar which after some more grunting and swearing (some baad stuff this time) and I realised enough thread was poking out to get a nut on!!! Got both on and tightened them up. Yesssss! That bugger took me about 3 hours overall. Must remember to use the crowbar next time.