Barney is 7 months old and on the advice of the vet, was castrated on Friday.  He now has to wear a cone collar until the stitches come out and I was told to only exercise him in the garden and then only on a lead.  My question is, how can I stop him going stir-crazy? He is still only young and wants to play, but he is crashing into everything with the collar and can't pick things up easily off the floor if we play 'fetch'. I am also mindful of not playing too rough and I'm trying to stop him jumping up and pulling his stitches. He is going for his post-op check tomorrow evening, so I will ask the vet then what I can do to entertain him, but in the meantime, I would be grateful for suggestions please.

I think most people who have a youngster neutered are in the same situation as you. :)
You could take his EC off while he is with you, as long as you watch him & he's not nibbling his stitches, you could also spend time playing with him as long as it's gentle & controlled. the main thing is that he doesn't jump up or leap around too much as this could pull on his stitches & also that he doesn't nibble his stitches.
You could take him into the garden with you for a little wonder around - you may need to keep him on the lead for this if he's likely to run around like a mad-man.
once you've had a PO check with the vet, you'll find if all is ok, you should be able to give him gentle lead excercise & take him for a stroll.
snoopy1

Thank you Snoopy1.  Yes it makes sense that provided we are with him, his collar could come off for a while, just as long as we can get him tohave it back on!! I am worried about the stitches as he is very keen to get to them at the moment and I don't want any problems with him pulling them and putting back his recovery, but I don't want to bore him to tears either as he is too young to laze around all day, bless. I feel terribly sorry for him, but need to ensure I don't go too soft on him as it is partly a behavioural problem that we have with him. Thanks for your advice.