usually a 9.5-10 in trainers
how do these size up width wise too?

For the winter my old 5:10’s impacts are a whole size bigger so I can get some decent socks on. My freerider pro’s are eights, which is my shoe size, they are only big enough for thin socks. All my Clarkes shoes I have are eights and have plenty of room for thick socks and more, so I would say that 5:10’s come up a bit narrow and short, plus unlike most other shoes and boots they don’t stretch with wear.

I usually go up half a size with FiveTens (or as robertpb said, a whole size for winter-only shoes).

There a new impact version (the “proper” one that looks like the old “Florence Magic Roundabout” shoe) if it’s that one they come up small.
bargain here: https://www.gooutdoors.co.uk/15924386/five-ten-men-s-impact-low-mountain-biking-shoes-sizes-7-12-15924386
Updated version is not quite as nice as the “old” ones, less lorica? “leather” more fabric and lace holes rather than loops, work well though, I had to go up a size. They do look open up though with use, maybe I shouldn’t have.
Nice and wide which is why I like em. The “Adidas” generation of five tens are a bit narrow for my spade feet.
I was thinking about 510s today, such a shame the VXi with flat sole (untreated area) has apparently gone. Those fitted me OK too and were “real size”.

Had a pair of impact vxi which were horrid.. Too narrow and too small (size 9)
Always used shimano before in size 9 with no issue.
Tried a pair of cheap freerider off crc the other week size 9 and they’re fine so make of that what you will🤷‍♂️

They’ve got smaller than used to be. I’d say if it’s a new pair buy ip 1/2 to a full size over what you know. (treat them like adidas)

Tight on width due to lace brace design.

Liked em but had to return

Yup, wish I’d gone up half a size , still breaking a pair in, comfy but not laced up tight.