It depends what you think interest rates are going to do - C&G SVR is currently BR+2%, but their Homeowner rate (which all new mortgages are based on) is 3.99% and (I believe) not linked to BR.
If you're on the SVR (like me), I'd stick with it as I don't believe rates are going to go up for a while, and then slowly (although I'm sure other ABers will have different views!).
If you're on the HVR, then I think there are lower fixed rates becoming available - although all with strings attached, of course.
Happy mortgage hunting!