I've built all three, the are four really, examples based on the drifter hull; the Britannia is the most stable of the three, not that the others are bad I should add. I have sailed mine in the foulest of weather and in relatively high swells without any problem at all, this includes Lake Windermere.
The kit goes together well and you should encounter few if any problems. currently all Mountfleet kits are being upgraded which should make the building experience evenmore satisfying and quicker.
LB