bp wrote:
HI,

Thanks for the replies.

Yes there is double glazing. I did think that there was a ventilation
problem. The previous owner has fittied a vent (air brick) at the
front room. It is high up - near the celing.

Also I checked the air bricks. Most were blocked. I have cleared
them. There are 2 along the black wall (i.e. along the alleyway).
However since the floor level is higher then the air bricks, someone
has created an opening to allow the air to flow. There was alot of
dirt etc in there which was blocking them. I have opened them now, bt
I guess I will have t wait and see if things get any worse. If not I
guess blocked vents were to blame.

About the removal of the paint, could I sandblast it off? Or is paint
stripper the best option.

I doubt if you could blast bitumen. Too rubbery.
I wouldn't pin all your hopes on the ventilation issues