Why not just offer a few ideas of survial type knives for the chap, 'ey? keep the 'whatever you have at hand' bs to yourself. The dude wants to spend some cash on a new toy, and asked for our advise on a few. options..
For £100 or under there are some great options mate, I wouldn't bother with anything costing more than that as you'll probably be worried about abusing/using it hard.
As has been said already, the MOD knife is decent at cheap at £50. probably the toughest knife out there untill you go custom! needs a litte sharpen job but it's a ebast after that.
For even less, at £30 you can get a Cold Steel bushman knife. Super tough and very lightweight for a solid metal knife! hollow handle too that can be stuck on a pole for spearing or filled with 'survival' stuff
again this knife is
tough! it'll handle almost anything and doesn't need any work out the box!
or for the higer end of that price range, the Ka-bar adventure potbelly is pretty cool. Now I don't currently own one, but I've heard alot of great things abotu it's chopping ability and tough blade!
This one goes for just under £100 I think and will be one of my next purchases!
hope that's the sort of info you were looking for mate!