What are the safety risks? I am no DIY expert but thought looking at it that providing the new flue is fitted with some type of sealing compound (to the biloer and to the wall/ internal chimney) then it shouldn't pose any risk?
I have a floor standing Potterton Kingfisher Mk II boiler that was in the house when I bought it and which works so well that I am reluctant (and too mean!) to replace it.
However the flue pipe that comes out of the top of the boiler and connect to an internal chimney is in bad repair and...