Electric combi boilers / solar panels / eco heating solutions

To add insult to injury they're suggesting to replace 10 radiators (!) so it's £3k after the BUS grant for us. Maybe just get a combi (when the boiler breaks in a few years) and let the next owners handle it in a few years?

This sounds more hassle and money than you'll be saving. Get a decent new combi and some smart controls, and leave the rest to someone else to worry about.

The combi quote from BG (yuck) came in at £4,300 for a 30kW Vaillant 830 (rear flue requirement limits us to Vaillant apparently?) and in the meantime I learnt that we don't need to cap off gas (as long as it's not used for heating) and can keep the gas-hob range cooker. So all in all the costs would be about the same (£3k + £300 for planning + £500-900 for structural eng stuff + chimney block) of course we'd need to repaint some walls where the new radiators are shorter and thicker.

The loft insulation top-up doesn't seem to be in the requirements list, granted it's a good thing to do and we should do it anyway and we will, but nice that we're not held up to that before the works can go forward.