Hi PJ,
Take a bit of time making this choice- getting it wrong is costly!!
Modern Boilers are all mostly condensing- they are more efficient, and government regs govern their use now I think. Big thing is, do you live in a hard water area? (south coast of England perhaps? if so, do not fit a combi boiler at all costs- they will clog up with chalk in a short time, then you probably will need a new inside unit( not being too tecky). Some may argue, and my plumbing experience is a bit out of date now(retired), but I would not fit a Combi anyway-have a look at this website for more info. One point I should mention, if you have a roof tank and a hot water cylinder, conventional boilers are for you. If you live in a flat, with no loft to fit a roof tank in, then a Combi might be your only choice. There are some plumbers on here with current experience who will be along to advise you I am sure, but this is a bit of info to be going on with.
Good Luck
Richtee