Replacing Randall 103 mechanical timer

[theo5]

Hi all, I have an old mechanical timer for my heating (Randall 103) which isn't working. The boiler comes on when I switch it to the on setting, but when I switch it to the timer setting, the clock doesn't actually turn (although it ticks), so the heating never comes on.

I'm considering replacing it with an electronic programmer. Is this straightforward to do, or is the wiring more complicated?

It looks like the Danfoss 103E5 or 103E7 might be compatible?

thanks for any help!