I had a quick google for 'Bembridge houseboats', naturally no pics of what I was on about but a couple of references...
'Bembridge houseboats include a motor launch, some landing craft, two former patrol boats, one torpedo boat' (& more modern craft)
Next time I go to Bembridge I hope I have the brains to photograph these WWII craft before they really do go !
As well as quite a few MTB's, MGB's etc at Shoreham, the last time I was at Haying ( Island ) Yacht Co there was at least one large MTB houseboat.
Andy