Hi Phillip,
Yep that was our video from the trip i did in 2015. I was told when i bought the yacht that it was from around 1975, however i think its a bit older than that, there is no plate or hull identification on the hull, it does seem a bit different from other MK1s as it doesn't have the enclosed head (head is under the V-birth and there is chart table where the head is on most tophats.) Also there is no mast bridge, just a metal plate as pointed out by some others on the site, there is reinforcement for the mast under the forward bulkhead.
Cheers
Nick