2014 Vauxhall Insignia water in boot

Water coming into the boot and down into rear passenger foot well. Looked for about 3 hrs after stripping out the whole boot trim and rear seats. Removed the rear fuse panel and saw water constantly trickling from a pressed out hole which was covered from the outside (before bumper fitting) with a piece of tape which after 8 years has failed.
I found a plastic cap of similar size and filled it with mastic placed over the hole and taped in position. So far so good. Only problem now water may have gone into wiring loom as central locking deadlocked all doors except boot and drivers door with key.