Tricky because your engine has a chain rather than belt. With the diesels we tend to replace the waterpump at the same time as the cambelt because it's literally right there attached to the same pulleys, so for an extra £30 or so it makes sense to do it.
As with anything though, the water pump is a possible failure part and will have a life span like any other replaceable part. If the water pump fails, your engine will overheat but if you get to it quickly enough you can get towed to a garage and have them replace it. It's a relatively expensive part to replace but that's only because of the labour involved, rather than the part itself.
If you're worried about it, get it done, but my advice to you would be to have the garage replace the timing chain and pulleys at the same time so that you know you've got brand new parts in the most important part of your car. As to get to the water pump they would have to gain access to those parts anyway, you wouldn't be paying much more in labour at all to get them all done at the same time.
