if its in good nick theres no real reason not to fit it if its done right.
Well its not going to be dne right is it, it doesnt conform to current regs, also would you buy something that contains gas, electric and water that could cause major damage and you know nothing about how it works, 2nd hand off e - bay, i wouldnt, FFS just get a new boiler tight get
the current regs are pretty much irrelevant. all he wants to do, i assume, is fit a slightly newer boiler with a slightly better performance. if he is willing to take a chance on buying a boiler second hand good luck to him, i still want him to get it fitted by a professional. i personally would do it too if i thought it was worth it as the linea is a good boiler and i can't think of anything i would want to buy new for £500.
i would want to have a good look at the system it came off first though, not that anything on the linea is difficult to change or outrageously expensive to buy anyway.