Hi,

I would agree "birch ply" works best for me. I purchase mine from http://www.alwayshobbies.com/ . It comes in small sheets (metric sizes). It's more expensive than buying large sheets from specific wood stockists. the above company also stocks hardwoods in thin sheets which are an ideal size for cutting out clock hands.

Wickes stocks some thicknesses of birch plywood in larger sheets however I haven't checked the quality yet so cannot comment on its suitability for clock making http://www.wickes.co.uk/.