Still, even at £600-700, it depends on what the car is worth to you whether you get it fixed. A couple of years ago, my Punto mk1 had a noisy input shaft bearing on the gearbox (it still drove fine), and I enquired about the cost of a reconditioned gearbox. The price was just under £600, and the car was worth probably £900-1000. I actually started looking at other cars.
However, each one I saw had little problems that I could see. There were puddles under the radiators and missing caps and messy battery wiring from bodged aftermarket alarm fitting. I soon realised that apart from the gearbox, my car was in pretty good condition, and worth the gearbox swap.
After having the gearbox swap, I fixed any little niggles. I also treated it to a good wash and a nice, new set of mkII alloys and tyres.
Turned out to be a very good decision indeed. Since the gearbox swap, I have done well over 40,000 miles with virtually no trouble, just the odd wear and tear items here and there. The only major work since was a head gasket replacement, which was only £300, less than 6 weeks' worth of fuel for me.
So the motto of the story is, if the car has been reliable and you are familiar with it, it is worth far more to you than Parker's will tell you. Wouldn't swap old faithful for a brand new Grande.