Pigeon Talk (web-based discussion forum) A friendly supportive site.  Click on ‘Resources’ at top of home page for information on basic and emergency care. If you need specific urgent information post your question on Pigeon Talk ‘Emergency Care’
Pigeon and Dove Rescue UK Excellent source of advice on pigeon care. Information about pigeons, woodpigeons and collared doves, illnesses and injuries, how to care for baby pigeons and more.
Helpwildlife rescue centre lists Location map of wildlife rescue centres UK. NOTE: not just pigeons/doves, so check descriptions.
Boddy and Ridewood Boddy & Ridewood is a very comprehensive supplier of almost anything to do with pigeons, except foodstuffs. Can order online
Royal Pigeon Racing Association Has a section for reporting strayed pigeons in the UK, and can usually trace owners