I've not had much time to check my post since I put it up. Thanks for your replies.
I'm surprised no one else has come across this disgusting stuff. It is indeed 'fowl' stuff
I've found a solution just in case anyone else has the same problem.
I don't have any TFR, however, a friend suggested carpet cleaning solution.
I had some 'Rug doctor' solution so I soaked it in that which did seem to get rid of most of it with some effort to work it right into the bristles. After rinsing it out I then soaked it in a strong hot solution of washing powder and water for about an hour again after working it right in. After rinsing it out and letting it dry it appears to have gotten it all out. It's nice clean and dry with no sticky residue.
So watch out for those little pots of bird repellent gunk. If you get even the smallest amount on a brush and are not carrying a spare pole or brush you won't be doing much more work that day unless you cut out the contaminated brisles