Stratford shower leak

Just bought a 5 year old Stratford. Parked in the drive and not moved. Empty grey tank and full fresh water tank. Day spent fixing shelves and looking around. Shower tray dry and unused. Following morning sees water in the tray. This dried then back to shelves and so indoors to bed. Following morning has water in the tray and exact repetition for 3 days. I did, of course pull the shower head and pipe out and place into a bucket to eliminate this. On close inspection I find the merest hint of a drain at the middle bottom of the plastic panel above the lip of the tray and supporting the basin. I presume this is to discharge water dribbling back down the shower hose, the possibility I had eliminated! I have an awful feeling that the tap or pipes behind the panel are leaking when the sun goes down and, of course, there is no access without cutting away loads of silicon sealant to dismantle most of the shower room, fixing and re-sealing. Has anyone been to this dark place or has a solution? A wick feeding into the shower drain is the best I can come up with.