Thanks for the reply.
Im using a Danfoss RMT 230 at the moment
From left to right there are four connections numbered 4-1-3-2 in that order.
Blue is into 4, yellow (with a red tape round it) is into 1, 3 is empty and 4 is red.
hope that helps!
Ive just bought a Honeywell DT92E wireless thermostat thinking it would be as easy to wire as a plug is... I unclipped my existing Danfoss to find 3 wires (red, yellow and blue and an earth (the latter is not connected)). The Honeywell instructions ask for lots more and I'm completely lost...