Coming clean
An extra bathroom and/or bedroom is the most popular format for a loft extension
One of the most popular uses for a loft extension is as an extra bathroom and/or toilet.
Plumbing and other services ares seldom an issue, and even a new toilet seldom presents serious problems.
A degree of imagination is sometimes required and our experience may well result in an arrangement you've not thought of. For example, a full-size shower cabinet may not always be possible, but a really luxurious bath might be tucked under the sloping eaves to create a truly arresting feature as in the top inset.
What is for sure is that you need real expertise to advise you on the best solution for your particular combination of space, services, requirements, and of course budget.