I'm viewing some flats just now (built 1970) for my 85 year old Mum and am looking for some guidance re ventilating the bathroom in the flat she's really keen on buying (Flat A). Sorry if this is a bit long-winded, but it’s the only way that I can describe the situation. I just need to know what my options are before I put the offer in.The property is in Scotland (just in case regs are different). The building is 2 storeys high and Flat A is a top floor property, with a flat roof. The bathroom dimensions are 7’ x 7’ approximately. There is a shower over a bath, loo and wash hand basin. If successful with buying Flat A, I would be taking out the bath and replacing it with a walk-in shower. The bathroom does not have any outside walls. It has been wet walled and a new ceiling has been installed and fitted with spots. The wall opposite the bathroom door is an outside wall.I know from viewing another top floor flat (Flat B) at the opposite end of the building that there was a horrible domed skylight in it’s bathroom ceiling. This could be opened by putting a pole into a tube attached to skylight, thus ventilating the bathroom. I’m presuming that this set up is the same as that above the new ceiling in Flat A.Back in Flat A, through the bathroom wall on the side opposite the long edge of the bath, is a deep walk in cupboard accessed from the hall. In this cupboard, at the far end, it has been boxed in (floor to ceiling) with wet wall. There are two square holes cut into this (about 4”x4”) set about 4 feet and 4.5 feet off the ground, but the holes are not aligned one above the other. They’re offset by about 4”. The Estate Agent thinks that's where the stopcock might be located. Being completely non-technical I didn't even think to check. There is a hatch to the roof void in this cupboard, but as far as I’m aware it’s not a very high space, so don’t think a person could get up inside it to work in it.Through the wall, at the short end of the bath, is a shallow linen cupboard. This is also accessed from the hall and contains the shower's (over the bath) electrical switch.Can anyone please provide any suggestions (not horribly expensive) for the best way of venting the bathroom. For example, could a ceiling fan be installed with some sort of ducting running across the new ceiling and roof void to the wall outside. Would simply fitting a fan on to this outside wall be of any use, by at least removing some of the moisture that will come out the bathroom into the hall? I would be employing a company to do the work, probably the same one who would replace the bath with a walk-in shower. Look forward to receiving the benefit of your knowledge ??