Lincoln's increase this year I think was also due to the fact it was advertised well in advance and in conjunction with Sheffield as an urban weekend, its inclusion on the front cover of Focus (yes, people do read it and in fact I think it's a rather good publication!) and also word-of-mouth. Certainly inclusion in the league will also have helped, don't get me wrong, but I don't think urban league point-collection is entirely the cause of the 100+ increase.
I think you've hit the nail on the head, there. All of those factors played a part, undoubtedly, and I think the Nopesport league 'double header' aspect encouraged a lot of people to travel and make a full weekend of it.
S.