Car won't idle or rev properly

The air flow plate should be easy to move - how much friction is there? I'm wondering if it is fuel starvation - the plate regulates the amount of fuel being injected.

Stinky, I think you were enquiring about brake servos the other day. If both queries relate to the same car, then the problems will probably be related. In this case I suggest that you disconnect the large bore vacuum lines to the servo and the ventilation control reservoir and cap the manifold ports for them to work through debugging the engine, then reconnect one at a time and test. Any system failure in either of these systems will allow unmetered air to leak into the manifold, creating havoc with idle ond acceleration.

OK so I've now changed the warm-up (pressure) regulator at great expense (it really looked like that was the problem) and it hasn't fixed the problem; if anything it has made the engine run a little smoother but it is still rough but essentially there's no power. It will start and run reasonably OK and rev fairly well but when trying to drive the car there is practically no power. The car will pick up and drive but I managed 15mph max and a slight hill caused a stall. It's as rough as a badgers arse, so with all other things considered I'm really looking for advice. My current line of thought is timing either ignition or valve timing. As the fault initially occurred suddenly I'm wondering if a timing chain has slipped. How on earth do I check for that? Help please guys.

Someone I know is sure it's the accumulator; can anyone shed any light on how the accumulator might cause the problem?

turned out to be a broken timing chain

No one could have diagnosed that over the internet! Shame you had to go through all that trouble before it was found though. I hope no damage has occurred to the valves.