I've seen integrated drop in bathrooms for new builds, but has anyone
installed one into an existing property? Where did you get it, was
access a problem and was it a success?

I have a Georgian listed building that could benefit from a couple of
en-suites. Last time I installed a bathroom in a listed building I was
told by the planning department that I didn't need listed building
consent for installing a toilet and bath into a room, but I did need
LBC to erect stud walls to enclose the new bathroom. It strikes me
that a pod might be considered as plumbing and not alteration.

Pete