Water leak showing on wall and ceiling

About 15 years ago i got my upstairs bathroom updated and converted , floor tanked , extra large shower enclosure with a Salamander type pump fitted into the hot press for the rain head shower and an old triton power shower.

When i had finished my shower this morning the slight lifting of wallpaper was made worse the wallpaper bubbled from extensive water showing on wall 6ft down so its serious and water dripping from light unit in sitting room.

No stains saying dirty water and assume shower feeds . Previous plumber was a bugger for dripping fittings which might be the case here.

How bad a job is it to find a bad pipe or connection and assume rip out shower unit walls to check plumbing?

Location of shower is above kitchen door ,no signs there and did have the old Triton over the bath 20 years ago before it was moved. Water leak is about 6 feet in from rear wall in sitting room with the shower above but in other side of wall. Inner walls of 60s house are compressed wallboard.

i got thinking to run the triton shower also to check if i still have a leak and if so might point to a shower tray issue and not behind the walls

Do shower trays have leak issues.