On Sat, 22 Sep 2012 20:55:30 +0100, Phil Addison wrote:

1) it is room-sealed - the old one isn't,

So will need an air supply from outside. How does this fit with a
conventionally flued boiler?

2) it is claimed 90% efficient, and even if that's an exaggeration,
it's surely an improvement over our cast-iron jobby which is no doubt
well less than 65%,

Wander over to http://www.boilers.org.uk and look your current one up.


--
Cheers
Dave.