I too have the same problem as RoverCat. My quick fix is quite an old remedy for older gearheads. I place a folded up piece of paper between the fascia and the switch and have had much success. This has worked all summer without incident.
I really need to replace the switch. Unfortunately the switch is part of the heater console and needs to be replaced as a unit. As a previous poster stated this will take time due to the entire center dash having to be removed.
As for the poster with the fan issues... I'm sure you checked all fuses including the box located under the bonnet. You can bench test the fan by removing it and placing positive and negative leads to the fan to see if it will operate. If not, you have a bad blower. The resister used to be a problem with the RRC not the D1 due to the fact it was located IFO the firewall under the cowl exposed to the elements.
1990 RRC, 3.9L, AUTO "Willow Pond" (Sold)
1996 D1, 4.0L, AUTO "Lucas"
1999 RR, 4.0L, AUTO "Belle" (Sold)