Thanks for your replies. I will definitely get the vet to check him again - especially his knees. He did see a vet two weeks ago but she just did a quick check of his heart, eyes, ears etc.
I don't think anything has frightened him - he thinks he's Rambo when he's out haha - when he decides he does want to go out he seems to enjoy it and bounces around. Its just that sometimes he decides he doesn't want to go. I'm not sure if in the morning its about leaving other family members in the house, but that wouldn't explain his reluctance in the day when no-one else is in. The dog walker usually walks him on his own but he has been out with her own dogs. Today she is bringing her own dogs again to see if that encourages him out.
The change has been gradual and I get the impression we are only now starting to see his real character. Sometimes he does look so sad though and I wonder too that he's a bit low. He went into foster care before coming to us so he has been passed around a bit
