Technically both the NSI ones are mini cash ISAs - they just market them in two different ways with slightly different names and give the higher interest rate to the one with lower running costs.
Over the counter try Natwest - 5% Some of the smaller building societies might go higher but you'd need to live where they have a branch or do it by post.
http://www.moneysupermarket.com/ISA/GuideToIsa s.asp
might help - it will give you a list for comparison and if you go into the details it will tell you whether it's branch post etc.