The pressure drops regularly,but i cannot see any leaks,Both ch and hot water work ok but after turning hot water off i get a lot of banging sounds and also whooshing sounds.tried bleeding radiators but they seem fine.
When using your central heating, watch the pressure guage, if it rises significantly when system gets hot, check the boiler overflow (should be a pipe outside) may be leaking indicating where the pressure is going.
If this is the case, it's an expansion vessel issue, needs re-charging/replacing