Cheers buddy, most helpful and most appreciated.
I was wondering why GSF sold a lambda tool! I'll see if I have a ring spanner to fit. Out of interest, is it easy to access if I can't get the car up in the air? From what I gather, it's on the manifold, but is it easier to get to from underneath? (I appreciate this may vary from car to car, I'm just interested whether there are general problems that need addressing)
Finally, how much driving is acceptable before I get this fixed? I know poor a/f ratios can knock lumps out of the cat, how long does it take before damage occurs? I'm not going to drive miles, but the car is needed for the odd trip in thew short term.