Hitch 'n Hilke in Bamford used to be a good stockist but I think they have cut back in recent years.I have a Montane Extreme jacket ? I think that's the model I have) not the smock and can no longer wear it above about -4C as it's too warm. My experience of sizing is that they are on the snug side which is what you want to trap the warmth.
I'm London based but have a car. I do most of my walking in the Chilterns or Herts, some in Essex. We get away to the Cotswolds or the Peak District or to Norfolk for a weekend once a month so I can go walking further afield. And then once a year I get up to the Lake District for a week. Oh yes I get a long to one or two OM meets.
Currently I've just finished the Peddars Way and in December I start the North Norfolk Coastal Path from Hunstanton. I find the fells hard work these days as I jsut don't get enough practice living in London.