How often should a water pump be replaced? I have seen a few recommendations in here that they should be done whilst doing a timing belt etc to save labor costs but not how often they should be done or how long they last?

As far as I know the pump in mine has never been replaced? (180k)

Water pumps last as long as . . . . . well, nobody really knows. They fail with water leaks or noisy/sloppy bearings.
Your pump may fail tomorrow, or go for 400,000 km.
(Unlike my old HX Holden which needed a new pump regularly, every 20,000 km. lol)

The general consensus on this forum is that at the second belt change, at about 200,000 km, the timing belt, idlers, hydraulic tensioner, seals and water pump are changed all together. Seeing you are paying someone to do the labour, might save money - if only the belt gets done and the pump fails a year later, you end up paying for the remove/replace labour twice.
If you do it yourself, you can decide what you do for yourself.

Sort of right, pump 200k, Pre tensioner only when needed