The main issue is that homes were designed to trap and keep heat in, rather than true insulation, which means that as summers get warmer, our homes turn into ovens, with no way to cool them down properly. Case in point last summer with UK temps hitting 40C and above for a few weeks.
Government are trying to kill off the old gas boilers though, with heat pumps being pushed very heavily, not sure if they're enforcing it yet or not though. Apparently they're also looking at switching out natural gas for a hydrogen mix, but that means having to rework a lot of the piping/valves as hydrogen needs much higher standards than currently applied.
1. It is unlikely that hydrogen will be pushed heavily by the UK gov because of the expensive pipe rework. The reason they're pushing hard for heat pumps is because of the Glasgow Climate Pact; they're on the hook to reduce carbon emissions or pay heavy fines. To that extent, subsidising heat pumps becomes financially less unviable for them than doing nothing.
2. Regarding the heat in summer; the houses insulate well but don't do much to prevent heat coming in from the windows during summer. There are some pretty useful half-fixes; mvhrs+insulation, or recessed windows/overhangs/sunshades massively aid this. For those who rent that's not much help though :(