Help with rounded off screw.

[Diwrnach]

Just been building my XPro I got from Mr Claus and started assembling the front, (part 5 in the instructions if it helps) and up untill then no problems with screws, but one of the ones on the top at the back, which is counter sunk hole, with round head screw, it just slipped and more or less totaly rounded off the hex.

Tried to baxck it out, but it just slipped, so took the whole lot apart again (it was the last screw) and sat looking at it trying to figure out how best to get it out.

Cant get pliers on it as its in the counter sunk hole, and cant see a way to put a slot in it either.

Thinking either drill the head off, then try and twist the thread out with pliers, or maybe trying to drill the whole lot out, but then have to use a M4 instead up the M3.

Neither seems an ideal solution and was wondering how you guys go about this problem?

Many thanks in advance.