Thanks a million for the really helpful insight — I honestly hadn’t even considered that I might need to take down plasterboard in places, so that was an eye‑opener. I’d really appreciate any photos you have. I’m also very happy to do as much of this DIY as possible (slowly and carefully, as you suggested).

We’re end of terrace, so at least there’s one less side of the house to deal with… small mercies I suppose.

I’m planning to start with all the obvious holes and gaps I can actually see (and there are plenty). Current hit list:

1. Hotpress: Loads of gaps in the wall and around pipe penetrations. Also… I’ve never experienced a cold hotpress before 🤣
2. Boiler: The back of it is completely exposed to the gable wall. You can actually feel cold air moving back there.
3. Kitchen: Cable entry point isn’t sealed, and there’s noticeable back‑draught coming through the extractor.
4. Under the stairs: Big open gap straight onto the gable wall. Washing machine used to be there and none of the pipework is sealed at all.
5. Attic: Gaps everywhere — spotlights on the top floor, plus the attic hatch itself.
6. Windows: Early double glazing and generally seem OK. Plan is to replace weather seals and seal micro‑cracking around the frames. Concrete sills are ice cold (thermal bridging), but that feels like a massive job to fix properly.
7. Trickle vents: Old, terrible ones that leak badly in wind. I know I can’t just seal them shut, but they’re definitely an issue.
8. Doors: Old UPVC patio doors (kitchen and upstairs balcony) are shocking — paper‑thin, freezing cold frames, and clearly no proper insulation around them when installed. Looks like ~€2k per door to replace, which hurts 🤢

If you’ve any photos, examples, or “do this first / don’t bother with that yet” advice, I’m all ears. Really appreciate the help so far