Couple of months ago, took my Y reg Vauxhall Vectra 1.6 in for a dose of preventative maintenance. It's done less than 60,000 miles, but has not had full servicing lavished on it in the five years I've owned it. I have changed oil and filters annually, but only by myself, an enthusiastic unskilled amateur.

So with ten years and sixty thousand miles looming, I thought it was time to replace the timing belt to avoid the horror stories of cylinder head/valve damage due to belt breakage. Took the car to a small independent garage which is handy for where I work. Couple of months of trouble free running were interrupted last week by a rattling from the engine area. Phoned to book it in for diagnosis, but car would not start to get it to the garage. It had broken down right next to another garage however, so I asked them to have a look. They could tell the timing belt was recent, but could also see how much slack was in the belt, and advised me to contact the garage who had changed the belt to put right the work they had done.

After inspection by the original mechanic, a failed water pump was found to be the cause of the problem. He is going to fit a new water pump to see if the engine runs with the timing belt back in place, if not we will have to find out the extent of the damage in the cylinder head.

Now I realise hindsight is a wonderful thing, but after researching the problem here and around the internet, the general consensus seems to be that during timing belt replacement the water pump should be replaced if only because the majority of the labour in replacing it has been done when taking the belt off.

So to my question, should I have expected the mechanic to change the water pump, or at least suggest/recommend replacement when I booked it in? Surely an experienced mechanic should be aware of the best practise around this issue? From my research this seems to be a common problem with many makes of engine, not just Vauxhall.

Should he bear some of the financial responsibility if the major rebuilding work I fear becomes necessary? How much is it likely to cost? The car (low mileage and fairly good condition notwithstanding) can't be worth all that much by now, so expense approaching/exceeding £four figure sum is hard to justify/afford, but not really in a position to buy a new car either.

If you've lasted this long, congratulations, I appear to have rambled on a tad.

Any advice would be appreciated, thanks.