Update
Not sure if your problem has been fixed and/or gone away but mine has. The problem for me was one of the thermonstats in the house. One controls all but one radiator which was fine - the problem was with the other which controlled the rad in the lounge and has a battery in it. This battery was on its way out. When I replaced it problem solved
Might just be a coincidence but has been fine for 3 or 4 weeks now.
Not sure if your problem has been fixed and/or gone away but mine has. The problem for me was one of the thermonstats in the house. One controls all but one radiator which was fine - the problem was with the other which controlled the rad in the lounge and has a battery in it. This battery was on its way out. When I replaced it problem solved
Might just be a coincidence but has been fine for 3 or 4 weeks now.