in my new (old) house i have a back boiler,would it be an easy swap to fit a combi boiler instead ( in a different place)and remove the back boiler all together?,or is it not that simple?

also what would be the best make of boiler to get?in my other houses i had worcester 28si`s fitted and never had any trouble at all
this is a 4 bedroom house with 7 rads at the mo,but will be having an extension done to add 2 more rooms.looking at something that could cope with 12 rads really.

any idea`s
cheers
dave