We needed one that does the hot water timing too, so ended up getting a Honeywell Sundial RF2 pack.
It was quite expensive, although we got it at trade price as my Father-in-Law is a retired plumber and still has an account with a local merchant.
I think it is similar to the Salus one, but has more programming options and as I say, it does the hot water too.
It works well – once it crapped out and lost the connection to the ‘stat. But we just did a ‘off and on again’, which fixed it and it’s not done it since. We’ve had it about 3 yrs.
It’s got a holiday setting so you can tell it to not come on for 7 days or however long and then it’ll kick back into life when you are due back.
It also has an Extra Hour setting that works like a limited time ‘override’ for the heating and/or hot water. We use that function quite a lot.
It is very easy to program – guides you through most steps and you can copy a program from one day to the next, so programming the whole week is very easy.