I managed to sort out my throttle cable problem. I fitted the brand new cable I bought from Rimmer Bros and I bridged the gap with some garden wire I found so the car is now drivable. After some road testing I had to adjust the tickover and the throttle cable but other than that it is running fine. There is more power and it doesn't struggle with passengers or when it is on a hill. (plenty of them in West Yorkshire!) The exhaust isn't entirely leak free. It is blowing at the tailpipe joint which is down to me not pushing the pipe far enough in to make a good seal. If the weather stays dry I'll tackle it tonight.
Edit: I've finally replaced that horrible aftermarket door mirror with a standard one. Definitely an improvement and the screw holes were in the right place as well. Just the passenger side to do. I've declared my mods to the insurance who wanted an extra £27. Better safe than sorry.