Stoat Mustela erminea. Key ID features are: its size, orangey/brown with a creamy white throat and belly. Stoats are larger than Weasels Mustela nivalis, and have a longer tail with a black tip. When alive, Stoats bound along the ground whereas Weasels run close to the ground. Length: up to 32cm, plus a tail of up to 14cm. Weight: 450g. Stoats often take down prey much bigger than themselves with Rabbits a favourite!
If all else fails use the rhyme that my Grampy told me: Weasels are weasily distinguished because a stoat is stotally different!
Here are a few photos (it was interesting to note how they have whiskers on their front legs!):
Stoat - full shot
Stoat - head shot
Stoat - feet
Stoat - black-tipped tail