Ok so you would probably want a low end graphics card, maybe a Nvidia 820m, just to future proof it a little, and a medium spec cpu. so maybe an i5 4300u.
Also to point out minecraft is a very basic game, and has very low minimum specs, I can run it on my 14 year old budget desktop, albeit on minimum settings.
You should probably spend no more than £500, but no less than £299. a good example would be the laptop here: click here it is a bit too overpowered, it should last for a good 5-6 years, if he moves on form minecraft, and starts playing more advanced games.