Thanks very much John. Unfortunately the exact model isn't on their website so wonder if it is either older or maybe imported or something. After a bit more research it seems like the other control is to vary the power. Any idea how this works? Just looks like a rubber diaphragm at the top.

Also, I have now discovered another issue. One of the connectors to the bottom air jets is broken (it is a sort of tee where one of the junctions has snapped off). I havd just put some solvent weld on to see if it repairs it but not holding out much hope. Can they be replaced? The pipes going into it are mainly flexible plastic and seem "glued" in. Also, there is a metal pipe going into it and then a piece of hose to the trap. I assume this is to drain the pipework but can't see what stops this happening when filling the bath. I assune once the air jets are on the pressure will stop it.

Thanks in advance for any help.

Lee.