I think the neighbours do have an air source pump, but they had that before they installed the panels. I don't know who they used - we used a company called Solarsense based in Bristol, who were very good. They do the solar for Worthy Farm and Glastonbury festival, so I took that as a recommendation... A 4 kw solar array with inverter and Apollo solar diverter was about £5k (no battery). We will be looking to get an electric car in the future but at the moment I still do a reasonable proportion of long journeys for kids at university etc which just wouldn't be realistic with a mid-range electric vehicle.
I looked briefly at turbines but a quick search on a site that calculates average wind speed by postcode indicated that it's not windy enough to make it worthwhile. Another one of our neighbours does have a turbine, but I suspect it's a diy job from the early days of alternative power - people use them to power free-standing pumps for water troughs etc, but I doubt it would make a significant contribution to domestic electrical usage.
Think carefully about how you use the power, as that will determine the decisions you make. My neighbours with the ovens and the electric vehicle need to use power outside main daylight hours as they have to fire up the oven at night time and charge the car overnight as well, so the battery makes sense for them. We mainly work from home, so can run appliances in the daytime and could charge a vehicle in the day as well, so at the moment the benefit of a battery would not outweigh the cost. If we fit an airsource pump at some point in the future, that equation might change.
But yes, keep it simple is a good watchword. If the manufacturers/suppliers can't explain to you how it works in terms that you can understand, be sceptical. Find a friendly local plumber/builder/electrician and see if it makes sense to them and whether they would be prepared to work with it if things needed changing or repairing.
Once you're looking at specific systems, there'll almost certainly be a Facebook users' group for it, where you can get a sense of how it's working for actual people in the real world outside the manufacturer's shiny brochure. Have a look at the Everhot Cookers discussion group to see this kind of thing done well - it's mainly people burbling at length about how much they love their cooker, but occasionally there's a problem and people offer solutions and then the chap from Everhot pops up on the thread to give advice. There are also lots of FB groups for sustainability and self-sufficiency, so you might find more detailed discussions of the relative merits of different setups on there.
Going back to your OP, you should be ok with double-glazed windows as long as you fit ones that are acceptably slim in profile. Buildingconservation.com is the website recommended to us by the Council's conservation department for sourcing reputable tradesmen for listed buildings. 'Like for like' is the key term to use in any application for listed building consent (assumign that's vaguely true of course).
They tend to look favourably on works that are likely to make the building more sustainable, as long as they don't radically change the appearance. If you do want to do something more drastic, they tend to prefer schemes that are obviously modern and contrasting with the existing building - what they really hate is anything that looks like pastiche. So a glass box conservatory might get the go-ahead, but upvc Victoriana notsomuch.