FIS is a waste of time in this instance, and will lead you into a false sense of security. Keep your eyes open, squawk 7000 and if you want, call for a RIS.
I regularly fly in the Yeovilton AIAA and hardly ever call them, but maintain a listening watch. The times I do call them are the times that I want a RIS, (going from A to B, hazy or something special going on, - exercise for example)....