Am looking to purchase a house that has a part finished extension.

The extension has the walls completed (But not plastered internally), the
windows are in and the roof is on... so it's and empty shell.

Now, I'm guessing that the current (6 yr old) boiler might not be man enough
to drive the 4 new radiators we'll put into the extension (2 rooms x 2
floors) so we would like to replace it with a brand new combi.

Question is..

current boiler is downstairs, and hot water tank is in the bathroom...
Could the new combi-boiler be installed downstairs or do they need to be
upstairs as they are gravity fed (or not?)...

Now...

If we can remove hot water tank from bathroom, and move things around a
bit....

Then I'd like to use both of the new upstairs rooms as bedrooms, not using
one as a 2nd bathroom like the plans show. If I dont wish to complete the
extension (internally only) the same way as plans showed, do I have to
inform the locally planning dept etc.... or is that just for external stuff?