Quite a lot of choices, which is always a good thing. I decided to go with Squad Battles: WW1 as my first choice and am really enjoying it. I had a minor victory in the starter scenario, may have had a major one had two of my tanks not become immobilised (one I drove into gas, possibly a rookie mistake).
Overall though, seems like a good game, I'm certainly enjoying it. I'll probably get a grand strategy title in a few months' time once I've played more of this game, but thanks for all the suggestions. I can see me probably getting my feet wet with Commander: Great War, as it seems to be more user friendly for less experienced gamers. But I'll see nearer the time (I'd really like to get into Strategic Commander, but the isometric view puts me off a little, I prefer top down).
But thanks again for all the comments, very helpful.