Cheers John - I bought a cable a few weeks ago just in case - was only £30 and is nice and free moving but not yet fitted.
I have put some PTFE spray down the throttle cable and it has made a huge difference to the drive, I can now pull away smoothly instead of at 3000rpm. It's still not great, but is good enough.
I did look at the pedal box to see if I could get into a position to get to it - and be able to get back up again - was a bit of a struggle but I think I may be able to do it without requiring the emergency services...although I pulled my neck getting out of bed the other week so who knows!