The 2020 winter heating season has started for some, we encountered this under a bath – daylight was actually visible right round the pipe and it was plumbed in 20 years ago! The space above was big enough for birds, bats and other vermin the get in, even wind driven snow. Tragic
Please don’t think that you are OK if you have an internal soil and vent pipe. DANGER! The space under your bath almost inevitably will be connected to the soil pipe boxing and this in turn will be open right through you house including into the first floor void and loft. Sadly cold draughts can blow in down it or warm air can blow out in either case the result is heat loss, a cold bath(room) and discomfort, with the accompanying higher than necessary heating bills.