I have this problem...well not so much as your mate cos my [penis] head :P isn't that big but I've still had condoms that were really tight and left about 2" of my penis out, left a red ring around my cock and I think restricted the blood flow. And then there were the 'pencildoms' that wouldnt even go over my finger...or even the tip of my penis. So I'm gonna take my gf to the family planning clinic and get her the pill or buy some bigger condoms...Magnum I think. She likes the natural feeling though, without a condom a lot.

Anyway your friend and his girlfriend should have at least one contraceptive in place unless they want to start a family (condoms, the pill, right time of the month etc)