Its a fleeting glimpse but I've managed to narrow it down. I've compared it to other sightings and ruled out the possibility of a badger, size and shape are wrong. Its too large for Mink and the tail isn't right for an Otter. Its movement and size are wrong for weasel or stoat which leaves Polecat.
Polecats are not a common species and if it had just turned round I may have been able to confirm it properly. Nevertheless I have sent the clip of to some friends and experts and the consensus is that it is a Polecat.
I now plan to do a bit of research into the species in the area... is it possible that its a wild polecat or an escaped polecat/ferret hybrid. Stay tuned for more info when it arrives.