Thanks for your thoughts all. My injury was about 20 years ago when I went down a small flight of steps, slipped, missed a couple of steps and stood directly on my ankle. Ouch! I have a very high instep too which doesn't help when finding a good fit of footwear. My son has definitely inherited that, as well.
I am going to Go Outdoors FOB, either today or this week, so will look at the Berghaus to see if they have any good offers on.
I do like the Altberg's Fremington's in that they seem lightweight and definitely suited for summer with a good price point, but I prefer the look of the Tetheras except they are a little on the pricey side. Ideally I want to try them on in store so might try a little hiking trip where they are stocked and hopefully pick some up, if I don't find anything suitable in the meantime.
Out of the Altbergs, I think it might have to be the Fremington's as £50 difference is pushing it a bit.