Can i have my combi boiler moved into the loft with the vent attached to the chimney pipe(under UK law)?

I worked for a gas company for a while and can recall people having their boilers moved to the loft but i dont believe you would be able to put the vent into the chimney stack as there is a chance that this would blow back into ur house the best thing to do would be to get a free estimate from a local corgi engineer