thanks for the advice, in particular regarding the room stat. i decided to get one and opened the junction box (LWC1) just to check the existing wiring first. i found that it wasn't quite in accordance with the instructions, nor was the pump wire in the boiler connected as its instructions said...
my house has a 12 year old system (i moved here just under 3 years ago). it consists of:
potterton profile 80e boiler
no roomstat (trvs on every radiator)
fully pumped
2 motorised zone valves
open vented
storage tank with coil inside for hot water
it basically works, but a few things...