Plumbing Problems in the UK? Ask a Plumber Now.
No not really because the fan creates pressure that switches the gas valve on and to ovveride the safety of the boiler is a bit risky with your health and insurance
The service engineers will refuse to work on it if its been tampered with and left in a dangerous condition.
Why not let the service guys look at it and see what they are going to charge, you dont have to accept the quote you can find someone independent to give you a quote.