Nelly Mozer x

depends when you want it to flower. any of the C cirhrosa ones for early flowering, alpina for march/april or the Montana ones [vigorous though] full summer the list is endless and for late summer I like the Tanguta ones.

Cartmanii "Joe" (possibly if it has a bit of shelter) - early, lots of small white flowers.
Duchess of Edinburgh - double white, very old (Victorian) variety - stands the test of time!
Apple Blossom (frost hardy) - lovely scent, smallish pale pink flowers.
The C. macropetalas should meet your needs as they are native to Siberia.
Or you might try some of the winter flowering varieties like Jingle Bells, Winter Beauty or Wisley Cream - though winter in Wisley may not be quite as nippy as winter in Angus ?

Thank you all for your recommendations have looked at them all and think have decided on this one.
http://www.taylorsclematis.co.uk/clematis-ruby.html

Very appropriate for us this year.