Am I really going to save £300...

zoominatorone

a year when when I get cavity wall insulation?

And does cavity wall insulation really make any difference?

The walls upstairs (semi-detatched house) are really very cold, and have water on them when we get condensation from running the bath, cooking etc. (no mould though)

Also, we have double glazing (there from when we bought house) every morning they are dripping with water on the inside (not between the two panes of glass). I thought double glazing was supposed to stop that happening?

Cardew

Cavity wall insulation will certainly make a difference, but not £300 a year.

Isn't 'up to' £300 the figure for a whole raft of insulation measures?

Double Glazing will reduce, but won't prevent, condensation forming on windows.

Condensation will form on any cold surface, if there is sufficient moisture in the air. Take a cold beer from the fridge to illustrate!

Ventilation and/or steps to reduce moisture will help with the problem - there are loads of advice websites detailing measures you can take.