Cheers guys, no culprits caught as yet, but seeing as the boat was taken back to its mooring by British Waterways with all their clothes and their computer on it they may end up turning themselves in! Apparently forensics are going to go over it.
re the earlier comment about window configuration being the same in the 2 boats pictured, my dad built them both, hence they are both backwards (easier to make a brew while sailing!), and the red one is his steam powered one which no thieves would get very far with!!!