Thanks again for the replies.
I have contacted the dog training school and enquired about 1-2-1 sessions. The trainer said that 1-2-1 would be a good idea, but that it wouldn't be ideal to stop the group sessions at this point as it is important that my dog is trained in the presence of other dogs too. I have already paid up front for a number of group sessions as well.
I have been feeding him before going to the obedience group, unlike I did when he was attending puppy classes, as the classes are now at lunch time. I just feel a bit mean not feeding him in the morning, but I guess just one morning a week won't matter? I do walk him before classes.
In response to Lurchergirl -I feed him on Purina Beta puppy, just twice a day now, and he has up to three 20-30 minute walks per day. I do let him off the lead if there is nobody about, as he isn't very good at recall if he catches sight of another dog or person. When he is on the lead I have been using an extender lead, but I think I should stop that if I want him walking to heel on the lead.
Josie x