The Lincolnshire Langtons are certainly the most well known, and longest established, as well as being some of the most recorded, but I think its a misconception that they are the most wide spread, and mathmatically the largest family.
If you look at the Langton surname distribution maps (there are some linked from the lostlangtons site) its clear that there are more Leicestershire/derbyshire Langtons than Lincolnshire, and also more from Lancashire, and Yorkshire, the maps show the neighbouring counties as having large numbers too which suggests a gradual spread outward. But even if the jump is larger (geographically) its just as often Langtons from Lancs or Yorks, or wherever as it is Lincs.
Unfortaunately alot of Langton families over the years have claimed an ancestry with the Linc. Langtons, probably because of the archbishop, but when you look at the evidence closely, its clear that there are many Langton family origins, each seperate.
The Lancashire Langtons are definatley not related to those of Lincolnshire. They were from Leicestershire originally, and the Leicestershire langtons are of course from the Langton villages in Leicestershire, which have a seperate origin. See lost langtons site for the evidence to support that.
I'll have a look for Hugh's illegitimate sons as well, I'm sure i saw i site which listed some a while back.