Does it need to be done or signed off by a registered gas fitter or a sparky?

You can wire the base unit with a plug if you want so I wouldnt think that you need to have a spark to sign that off.
I fitted one last week in my house. The remote unit just screws onto the wall. The base unit needs 240v so I wired a lead and plug onto it and plugged it into the same socket as the boiler. The two wire link into the boiler was zero volts on my boiler so just wired it into the base unit.

works a treat.

Gas fitter, sparks don’t like touching boilers

They don’t have to be a registered as it’s not messing around with the gas flow, just the electrics. But if you don’t know them you’re better off with a fully qualified fitter who has experience with your make of boiler.

Don’t call British Gas to do it or your grandkids will be still paying the bill.

Or as above if you are reasonably competent you can bosh it in yourself.

Just had a closer look and the crude timer pulls out and plugs onto the main board with three wires into an FCI connector to turn it on and off. Simpler than I thought.

you’ve saved yourself a bit of cash then.

Might as well spend it one something shiny for your bike. 😀

Part P may be more applicable tothe installation. Is the boiler in a kitchen or bathroom?

Boiler cupboard in between bathroom and kitchen.

The Honeywell that gets recommended everywhere seems to switch the 240v on/off as required. That wouldn’t work as boiler supplies hot water on demand as well.

Jam – shouldn’t do, assume you are talking about a combi here, all prog room stats should be fine.