Greetings from South Oxfordshire.
We are waiting to exchange on a very tired (actually unliveable), 1960s bungalow. It needs gutting and extending at the very least. We are also considering demolition and building to the Passive House "Classic" standard, especially if we can get planning permission for a 1½ storey home. It's likely to be all-electric, so "Plus" might be achievable. We're not too bothered about certification, except as a means to achieve those ends.
I have renovated a couple of Victorian properties and read a lot over the years, including quite a bit on this site, but have never attempted anything of this magnitude. Apologies in advance for stupid questions!