A we glock is a good first sidearm for around that budget (can buy them second hand with 1 or 2 mags for about £70) bit like an m4, most people have one, but in the same way wont do you wrong. We is ok for pistols but avoid there 1911's like the plague with tm it would be hard to go wrong by. I'd recommend finding a pistol you like then asking about it on here.
Always bad to buy something and be told it's useless