First off - if it's the actuator which is at fault, then all 3 actuators would need to have failed to experience your type of problem - which is unlikely.

There are 2 relays actually: the one in the driver-side door switch and the one in the relay-pad above the fuses. I've seen problems with both.

Taking the door-lock-switch off is pretty easy actually. You remove that one screw and pull it sideways so it disconnects from the vertical-rod that connects to the door-lock. Inside you will find a heavily-varnished circuit-board, a large sliding switch whose tracks tends to get dirty/eroded (if you're lucky that could be your problem) - and the relay. The relay contacts are a problem - wish they'd used a larger one. To clean the sliding-switch I had to unsolder the relay so that the slider could be removed. That also makes it very easy to clean the relay. In fact, thought the relay is a double-pole, double-throw one, one set of contacts is not used - so I ended up swapping the contacts and in effect getting a somewhat new relay.

Having said all of this, I believe one of the fuses control the central locking mechanism - so check that first. The central-locking relay (near the fuse-box) contacts also tend to get hot enough to melt the housing under the relay that holds the spade-connectors in place, leading to weak connections that further heat up the relay and cause malfunctions. So check that as well.

Finally, for all those out there who have a loudly-chattering-door-relay problem whenever the central locking is locked/unlocked: I had this problem for 8 long years. When it got cold, my trunk/boot/dicky actuator would not unlock until I'd locked/unlocked the driver-door lock a couple of times. Changed relays, fuses and the door-switch to no effect. Finally found a bad main-ground wire from the battery to the body: after fixing this, chattering is no more. Strange that this was the only electrical problem I was experiencing considering how bad the ground connection was.

Noel