A couple or three given the weather at the mobut dont get too hung up on the word base layer you could end up paying top money when something else would do.
If I wore a night vision this morning I would have a turtle neck base layer (nike or adidas the ones golfers use) long sleeved winters cycling jersey kind of roubaix type thermal and that would be it but everyone's different +1 on the jacket its an excellent jacket albeit a little on the bright side for me
http://www.direct-golf.co.uk/golf_c...sey_turtle_neck_golf_shirt_shirts/p11836.aspx something like this but you can get them cheaper at sports direct or on ebay I paid £19.99 for mine but they are nice and snugly