Thank you Andy for your reply.
On the advice of RPRA here in England (after having no idea of who might be a pigeon fancier in my local area as all we get here are feral pigeons) I took the bird some 5 miles away and let it go in open fields yesterday morning.
I haven't seen the bird since so I am hopeful that, having been suitably fed, watered, rested and cared for in the past week it has decided to return home!
Thanks for your interest and advice.