Even before the ECU you need to check some of "the usual suspects". The climate control ECU is not one of the ones that typically and commonly goes round the bend, though it does happen sometimes.
Make certain that every fuse in your car is functioning. I think yours will still be the glass tube type and, if so, use a multimeter to do a continuity check across the ends of the fuse. Make sure that all the clips into which they fit are gripping them firmly.
Check all the relays, particularly the fan relays. Over time these tend to develop corrosion at the connections in the engine bay and get wonky. Popping them out and cleaning the terminals with steel wool is one of my favorite ways to get rid of oxidation/corrosion. I received the following advice regarding my Shadow II, and it applies at least through the early SZ series cars as well I believe, "There are 2 fuses on the ledge under the passenger blower motor housing. 1 is dummy, other is for ACU Fans, and THE fuel door RELEASE. If your fuel door solenoid is inop(key OFF only), then you go there first. ALSO, Check every fuse in the fuse board with a test light.n Not just looking at the label."
There are chronic issues with both the flap actuator motors and the bushings at the flaps themselves decaying. Also sometimes the cables become sticky.
Were I a betting man I'd suspect you probably have some bushing issues accompanied by fuse and/or relay inconsistency.
You might also want to consider joining the Rolls-Royce Owners' Club (US)
and getting involved with your region.