We are having a very wet windows which has caused the area under the window to become mouldy and wet and we are finding that the ceiling area above this bay window is also very wet.

Does this happen all year round ? or just when it is Very cold and damp outside ? If it is the latter It is Condensation

It could be a number of problems. 1. It could be the drainage in the frame (if u-PVC double glazed) could be blocked. Resulting in moisture build up. 2. If double glazed the seal on the unit could be broken. 3. It could also be that the seals on the outside of the frame have become defective. Any of these issues can be dealt with quite easily. The worst case could mean a new window. I hope this helps.

would check the roof covering of the bay to make sure there are no cracks in the covering, depending on if its a top bay or ground floor bay would be checking the felt on the main roof leading onto the bay or the lead flashings going into the wall, hope this is of help alex

If its the ceiling above the bay window it must be your roof leaking, so get that checked first.

sounds like condensation. do u have vents in the tops of the windows as this would help. once u have sorted this u need to wash the mould of with fungicidal wash as the mould can be dangerous to breathe in.

Poor ventilation see it all the time, Mould will certainly need to be cleaned using mould kill products, DONT use bleach McLean building