Notts (Hollinwell) is an absolute must play and if in the area for a while, probably worth a couple of days golf at the least.
As already suggested, also to the north of Nottingham are Sherwood Forest, Coxmoor and Lindrick.
Woodhall Spa is well worth a trip, but as for Ganton, its about 2 and a half hours away and if willing to travel that far your friend could just as easily play some of the London sandbelt courses (Sunningdale, Wentworth etc) or a few links courses (Brancaster, Hunstanton) which are probably just as far away.