-
What Airhead said. Very good advice.
I hired a core drill myself which came with an isolation transformer. It's a tough bit of drilling depending on your wall construction. Took me maybe an hour or two on a Victorian brick house.
I'd get a fan instead of using a dehumidifier. Envirovent Silent 100 works quite well for me. You want your bathroom door to have a gap at the bottom to allow ingress of air.
Someone might suggest getting a fan above the shower head, but often this is not an easy solution.
No idea how much you'd pay to have this work done, but if it were me doing it (and I'm slower than a professional tradesman), I'd want a full day's pay, so something like £200 - £250, I guess.
righto.
cost of "getting someone" to do the job (with parts etc)
vs
cost of a shit hot dehumidifier and having ceiling replastered and strange shelf thing in there levelled out. and using window plus bleach.