At present the indoor pool (presumably) forms part of the main property.
You would have to legally detach it from the house deeds,and even if you CAN do that,I doubt whether a council will give you permission for change of use of the building to residential use.
You will definitely need planning permission for this(sorry) and I think (off the top of my head that this unluikely to be given for the use that you require.
Also wouldn't the professionals who let the house object to the removal of the swimming pool from their lease,and would they not also require a lowering of their rent to cover this..
You could live in the main house as a maintenance and security person,but not,I feel in the converted pool house(for the reasons given above).
Why not phone your local planning department,and just tell them you want to convert the poolhouse into residential accomodation,and see what they say.
Sadly,I fear it will be in the negative.