Well there are defo double figure barbel in the Avon, But I'm not sure they will 'crawl up your rod'!
Spent most of last summer and this winter targeting Babel on the Avon without great sucess, but they are present.
The Barbel on the Bristol Avon are on average larger than some other rivers, but not as abundent so need to be traked down. Some venues have seen large angling pressure, and as mentioned previously people are quite touchy about their fav Barbel swims and tactics! Its quite a touchy subject!
send me an e-mail and can help you with a few pointers that Ive been told by people far batter Barbel anglers than I'll ever be!