I've actually put it back the way it was now, and still no power to the boiler. I wish I'd taken pics first. I did as is described above though. It does look as though the boiler is powered via the receiver.
I actually went ahead and tried but now I'm not getting any power to the boiler. I've home emergency cover and someone's coming round, but wonder if there's an easy solution 've missed.
Thanks guys. No it's definitely a Nest E. There's a switch next to the boiler which appears to power both the boiler and the receiver, so one of each of these presumably is the boiler's and the others are for the receiver. I think I'd best get someone in.
Im replacing our Salus rt300rfwith a google nest e and wanted to triple check the wiring. I've attached a photo of my salus' wiring. I think Im right in saying that it should be as follows:
COM (grey) to: Nest Heatlink (2) Heating common
NO (black) to: Nest Heatlink (3) Heating call for heat...