I've just had my Baxi Boston 2 Boiler serviced, it's 17 years old. The boiler looks in good condition and has been passed as safe to use. However, the heat shield (looks a bit like a narrow wafer biscuit) has broken / fell off the front burner plate. I don't want to buy a new boiler, can parts still be bought for this and if not is it safe to use indefinitely? The service engineer was pushing to invest in a new boiler.