Im needing to replace my old (15yr) Danfoss RMT230 Room Thermostat and thought this would be easy. Sadly I've failed at step one and cant even get the old frontplate off. The dial comes off fine and there are no screws to be seen holding the frontplate and backplate together. I've seen instructions that suggest inserting a screwdriver upwards in a slot at the bottom presumably to release a catch as it doesn't suggest twisting the screwdriver. But even with considerable pressure nothing seem to work. Am I missing something. Any suggestions welcome