Help with ID please

[ohgreatstew]

I saw this out walking on open downland, there is a hawthorn hedgerow along one side, and I saw a mammal of some kind, I have to say my first thought was chipmonk!
obviously not, but it most certainly was not a grey squirrel, although it ran exactly like one, with it's tail big and bushy, about a foot long inc. tail, appeared to be feeding where the sheep had been standing for the night, and ran into the hedgerow as I walked along, sadly it was far to quick for me to picture it, could it have been a red squirrel on the south downs? Or is it more likely to have been a stoat or a weasel?
Either way this is a first, I walk this route twice a day for many years and have never seen anything like this.

[caernerch]

first thing that sprang to my mind was edible dormouse (glis glis) but it's a way of its patch as far as i know - the books have it as in the triangle of Beaconsfield, Aylesbury and Luton.
Size Head & body length: 12-20 cm (2)
Tail length: 11-19 cm (2)
Weight 70-250 g (2)
i'm a northener so I would have to defer to anyone with more experience of the area.
caernerch

[Dogghound]

Sounds like a small mustelid to me. Stoat or weasel.