hi Wombles, I would say a one year guarantee on labour would be in line with suppliers and consumer guarantee act but its up to you. I recently had a leaking P. Cocks cyl leaking after 3yrs, even with a 10year guarantee they only covered the labour to remove and replace for one year, clients are not happy as nothing done to fix it yet. I went around to make sure it was not an install problem and that was my only input. If it had been my work at fault I would have fixed it without charge but it depends on the client whether you would do that or not, cheers