Digital downloads at GAME from £2:
Ace Combat Assault Horizon Enhanced Edition £2
Just Cause 2 £2.50
Enslaved: Odyssey to the West - Premium Edition £2.50
Ace Combat and Just Cause 2 are stated as Steam versions. Enslaved does not specify on GAME's webpage whether it's Steam or not but I think it will be.
Dark Souls 2 for £11 is probably worth a mention too.
Sorry I messed up direct link to PC downloads page and it won't let me edit now, Please see links to each game in 1st post below: