Re: Remove only bath and replace it with a standalone shower: Building Regs? House Va
There is a part of the Building Regulations dealing with drainage and with hygiene. However, unless your friend is going to do something improbable, it is unlikely that the Building Regulations will have an effect -
the most important aspect is that a house is supposed to have a shower/bath with hot and cold water. If the work is only internal (i.e. not involving digging up sewerage pipes etc., you'll be fine.
As said the other thread covers the other aspects you enquired about.