The only issue with water pumps was on the V6, Ford used a plastic impeller on the early one's, and some failed because they used cheap plastic, but that was only on the mk1 and early mk2, once they were made aware of the problem, they revised the impeller and used better plastic, and that solved the issue. Stupid thing is, they used the same engine in some Jaguars, and used a metal impeller, so on all three of my V6's, first thing I did was change the water pump for a Jaguar one, more for peace of mind than anything else. But that's not an issue on the 4 pots, was only on the V6, and by the time they started making the mk3, they were already using the revised pump.

As for anything likely to go wrong, not really mate, the only well known issue with all mk3's was rear subframe bushes, that was a common issue on everything from the bottom of the range to the ST220, but the mk3 petrol is a very good car if it's been regularly serviced and maintained, the diesel on the other hand, that was a different kettle of fish lol. But yeah mate, just do the usual checks, and make sure it's got a decent history, and you shouldn't go far wrong. I've seen a few 2 litre petrols pop head gaskets, but that wasn't a known issue with them, any car can pop a head gasket, for a number of different reasons, but head gaskets checks will be one of the first things you will look at when viewing any second hand car anyway.