We have mould spots in the corner of our downstairs toilet.. started with just a small amount but now have lots. Not a patch of mould but lots of small spots. the room is on the outside corner wall of the house. I think it was once an outside toilet but a porch type building has now made it inside the building. Can I just paint some damp proof paint over it or is it a more serious problem. we only bought the house 3 months ago and there was no sign then

There is probably moisture inside the wall. Take a look at the outside of the wall to see if you can identify the source of dampness. Maybe leaves are piled against the outside of the house, or vines are growing under the siding, or a downspout is splashing against the house when it rains. Or perhaps you have something leaking down inside the wall from upstairs. You will probably need to remove a bit of the wall from inside. If it's drywall, this isn't very hard to do, but start with a small hole, maybe 6 inches across. If you find wet insulation, you should enlarge the hole and remove all of the wet stuff. Before you replace all of the wet stuff with dry stuff, you need to remove the source of the dampness. It could also be that this corner is poorly insulated and gets lots of condensation from the shower. Good luck, Al K