Forget about looking in those boxes.
You need the main board connection block.
240V mains in
240/12V switched for the thermostat or control.
It’ll be in the manual for the boiler.
You really are making it much harder than it needs to be.
All the Hive does is either open or close a demand circuit. Nothing more.
You just need to identify which 2 terminals it is.
RTFM or post up here the exact model you have so the ones of us that have an idea can actually help you instead of having 10% of the necessary information from the 2 pics you’ve posted.

Edit – 3 pics.

Here you go.

Page 29. Fig 32
L&N for receiver tapped from L&N in
Switching on bk1 & bk2

https://www.baxi.co.uk/our-boilers/combi-boilers/-/media/websites/baxiuk/files/product-literature/baxi-platinum-combi/baxi_platinum_combi_installation_and_service_manual.pdf?la=en&hash=9DFCE6C1D45832C8E7919E71C262846D1F622214

On second thoughts, don’t do that without making it exceptionally clear at the boiler that there could still be live feed to it from the Hive unless the Hive is also powered off. That’s why the instructions show the live feed coming from the boiler.

You need to put a link between live and 1 on the backplate of the hive receiver. The receiver will switch from 1 to 3 when the hive thermostat is calling for heat. Keep your time switch at on, at the boiler and use the hive thermostat set your on/off times and temperatures.

I tried putting a link between live and 1 which was labeled as COM on the old stat and it still doesn’t power on the receiver as I’d expected and read other people had done with similar 3 wire set ups.

So looks like I’ll have to wire it from the terminal block in the boiler.

Edit: as per what regenisis has added on his post, thanks

Also I noticed on the boiler wiring diagram it shows the stat as having the two switching wires and a neutral… I thought the COM wire was the live.

Not sure that makes any difference to what I did as I wired it where it said to wire COM anyway

I’m not trying to be rude or insulting here, but everything you’ve posted in this thread shows a fundamental lack of understanding of how electricity works, how your boiler works, how the hive works, how the old thermostat works. I wouldn’t be in the least bit surprised if you’ve somehow managed to fry the Hive receiver by now.

The very first reply on this thread advised you to get someone in who knows what they’re doing. I’m sorry mate but you need to follow it.

I’m not as incompetent as I sound I just struggle to explain things the way I’m thinking about it sometimes.

Anyway thanks for everyone’s help, got it all up and running now was simply a case of wiring to the boiler where I had a live feed to use and the knew 100% what the terminals were, as it turns out the wires swap colours 3 times on the way to the old thermostat!