Yeah Orc's nest is definitely the most central (and closest to your friend - in fact it's on Shaftsbury avenue) but it's not cheap
and it's not really very good.
Is hands down the best games shop in London that I'm aware of. Decent prices, good stock, knowledgeable staff.
Closest is Orc's nest. Not best prices though.
Not the worst either. While I'm a regular Leisure Games and I love them to pieces I've picked up several games at Orc's Nest for the same price as LG. You can always search online at check the prices. LG has also told me games are unavailable but then they've been at ON which is why I've known the comparative prices.