If you get no joy finding a courier it might be worth your while phoning the RPRA (01452 713529) and ask them if they could put you in contact with a local fancier who could collect and house the pigeon till you get a courier sorted.
http://www.distancesfrom.com/gb/Kincardine-Bridge-latitude-longitude-Kincardine-Bridge-latitude-Kincardine-Bridge-longitude/LatLongHistory/7577631.aspx The Latitude of Wallacestone is 55.9769. The Longitude of Wallacestone is -3.7341. The Latitude of Kincardine Bridge is 56.0643. The Longitude of Kincardine Bridge is -3.73. .
Canker but I have seen pigeon pox inside a pigeons throat that looks similar but this is normally accompanied with pox on the outside of the beak and eyes ceres.
Handle he's birds race marking, are yours heavier or lighter, are they of a small type/lighter framed. A couple of things that may help answer your question.