It will almost certainly require a sealed system - so the current F&E
tank and associated pipes will have to go, and be replaced by a pressure
vessel and filling loop. [Anyone know whether you can still have a
vented system with a new condensing boiler?]

Yes. No problem, although not all models are suitable. My last house had an
condensing Ideal Icos on a vented system. However, a sealed system is
superior, and I would advise taking the opportunity to change over.

If any of the radiators or pipework are suspect, the additional pressure
may well finish them off.

I see this as an advantage of the sealed system. Better have the
radiators/valves etc. blow right now, with a plumber in the building. If the
sealed system at 2 bar causes a leak, there is only a few months left at
atmospheric pressure, when they might start leaking during Christmas dinner
or when you're off on holiday.

Christian.