The main criticisms I have for the original EOS-M are: slow focusing and poor battery life. I ought to use it more to be honest.
Thanks. I'll look at the AF below, but regarding the battery life, this isn't much of a worry for me (and never has been for any camera), as I'll invariably carry 2 or 3 spare batteries whenever I go out with a camera.
But to answer your question, in order, the M50 II, M5 and M6 II would be the attractive options.
But the AF system is a bit 'last gen' and overall the performance in challenging conditions becomes sluggish to the point of frustrating.
But I suppose it all depends on your usage needs, and you might be happy with an M (and they're rightly affordable).
However, you might also want to look at a free test drive of the new R50 or similar, as that's clearly Canon's future (they do appear to be a similar size to the M models with viewfinders)
Thanks for the feedback.
The more I've looked into this, it seems that the main improvement through the M range has been to the AF, and also the increase in pixel count from 18Mp (M) to 32Mp (M6II). That's an increase from
5184 x 3456 for the M, to
6960 x 4640 for the M6II
As I am specifically thinking of using this camera for exploring "street" photography, I don't think the increase in pixel count is so relevant, as I don't envisage creating large, high quality prints, and would hope that even with moderate cropping, the quality should still be pretty decent.
Regarding the AF, the M is obviously pretty sluggish, but despite the M6II being the latest in the series, it would appear not to be that impressive (Phil's comment about it still being "last gen"), and I certainly wouldn't expect it to be anything like my R5!
Given the above, (and contrary to my normal desire for more/new kit), I think that what I'll do initially is to take the zero cost option, go out and about with my original EOS-M with 22mm f2 pancake lens, and adopt the approach of removing AF from the equation completely by pre-setting the focus distance on manual and see how I get on. This way, I can always change the approach in future, and even if I need to do that, I'll only have used up some time, and no doubt gained some experience anyway. Looking forward to it, and it'll be good to dust off the EOS-M, which has been sat in a cupboard for a few years!
Many thanks for all input - it is much appreciated!