Yeah water pumps are normally replaced with the timing belt, it can be that it has been over the period but not over the milage, so I would get the bîg service done.
A VW mechanic is also doing servicing as the mkIv Rabbit has the same engine and same chassis base.
150hp engine is pretty safe, 180hp if not well maintained or threated can fail (a small percentage but still), 225hp version are safe too.
A good mechanic can work easily on the cars, as the 1.8t are pretty bulletproof and easy to service, so you can safe a bit on that part later. But it should be one with at least a bit of knowledge with VAG models.
Look at the hoses, after that age they can get a bit leaky, depending on the climate they live in. But that's easy to see, check
Also if there is a VAG dealer near by, you can (at least here) give the chassis number (VIN) and check what has been done on the car, see if it had been involved in a crash, well serviced,...
Mine 1.8t never had a problem, I have around 120000miles on it and the first turbo. So if well maintained, they are still going strong
Thinking about it, around the 120000miles it needs the big service anyway so water pump gets changed anyway
I also saw 1.8t easily crack the 200000miles marker without problems.
Other than that, it's the normal things to check out at 120000 miles, suspensions, bushings,...
, do it you might find it very cheap) It gives you a good overlook over safty features and the like
