Thanks for your reply Dan.
Would you believe the bloody display screen has come back on! Yes, the batteries were in the right way round, I'd already checked that. I have to say this is the most complicated thermo/control I have ever had to use! It took me forever to work the damn thing out; I...
I have just changed the battery in the Salus 500rtf. The screen is now blank and I can't get it switched back on! I am sitting in a freezing cold house (I live in the North East of England). Please HELP! Thanks Denise