Deprnds on the car but a modern interference engine is almost always a right off, £500 seems way below the cost. I had a timing belt fitted to mine four years ago, everything checked out fine, new tensioners, new idlers and water pump fitted. For some reason one of the new idlers seized after 14,000 miles. The only sensible thing to do was to find an engine with as low a mileage as I could. Found one in Norwich with 13,000 miles for £300, had to pick it up out of a car rear end bash. I did have contacts though. Got no help from idler manufacturers. Check out the cost on ebay, I found around £1,800 with 60 -80,000 miles.
The good lady drives the posh car, I only have a run around for work. It's not worth much more than £500 so if it is fucked then I'll go down the scrap it and get another route.