The issue, for me, is that people talk of "permanent summer time" as the answer, sort of forgetting that the clocks are set based on lots of measurement at the Greenwich observatory and hence why we have Greenwich Mean Time. It is summer time that is the "anomaly" and it only makes sense to me to be on GMT all year.
This assumes stopping clock changes is a good idea, and that seems to be a matter of debate, but one which is leaning towards the idea of not doing it.
So, some thoughts on why, to my mind, it is obvious we stick to GMT all year.
The matter of definitionIt is called GMT, and is generally the high sun at the middle of the day at 12:00. It would be crazy, IMHO, to have the mean time over Greenwich as Greenwich Mean Time plus one hour.
What would we call it?We can't call it GMT and it makes no sense to call it BST as not only summer time. It won't be UTC if +1, so actually we need a new name. That is more of a pain that you realise as it is a lot of software and all sorts. UKT maybe?
It only matters in winter anyway!In summer we have more than enough daylight. Yes, moving some "unused" daylight from early morning to evening is vaguely helpful, or was before the invention of street lights. But what matters is Winter.
We tried a permanent summer time in 1970 and it did not go well. We know GMT in Winter "works" well enough and fits around schools and so on.
Changing what we do in Winter (by making permanent UTC+1) would be way more problematic as we simply have less daylight to play with. Changing in summer (by stopping BST) is not an issue as we have daylight to spare, so to speak.
Give UK an advantage?There are a lot of things that log in UTC, and confusion over UTC and local time happen all the time. Heck, even the Amazon app gets the order date wrong all summer because of this. BT get this wrong in their XML in lots of places. There is an advantage for the a country that stays on UTC+0 as their time zone as all UTC logs will be local time, and simpler for everyone.
Some have even suggested that UTC should be moved to the middle of the Atlantic so no country is UTC+0 and hence has any advantage. Let's give the UK that advantage.