winter training/commuter bike with discs?

naffets
naffets Posts: 72
edited November 2015 in Road buying advice
hi my trusty winter hack is falling to bits and in need of money being spent so instead of spending I was thinking maybe new bike over false economy,
my existing bike is ally frame carbon fork with shim 105 and basic mavics
I am thinking of discs whats peoples thoughts on disc brakes?
I don't really want to spend more than £600-700 wishful thinking.
hoping to pick up something up in the sale ? theres a Saracen tenet 3 going for £399 from a grand any good??
would prefer something not too heavy as only lightweight myself and bike
would have to do around 150 miles a week .

all info and thoughts much appreciated