hi iam thinking of replaceing my old boiler which is a glowworm radiation boiler. for a direct replacement which i have been told is a flexicom18 hx, the only thing i have been told to alter is the flue, does this boiler have a built in fan to extract the gases, also is it worth putting a room stat and cylinder stat in the system, has i have just got a external programmer at the moment which can be set on timed or manual and a valve which if shut you only have hot water, or open you get heating and hot water.