1) When someone knocks at the door, he almost flies across the room, jumps up on the sofa and sits on the window sill barking and looking who is at the door. I read elsewhere (on the Spaniel Trust website I think) that this is a leadership thing. He is the leader and greeting the intruder before we do.
I wouldn't say he is trying to be a leader. Protective maybe of his home and owners, nosey and excited too.
2) He sometimes (not always) when we have finished our dinners (say we are eating off a tray in the lounge), if we do not take the trays out as soon as we have finished, he will start barking as if to demand that we take trays out so that he can see if he has some leftovers. This suggests to me that he is being bossy but I know that others disagree with the whole "pecking order" scenario. Needless to say if he does this, he get nothing.
He is communicating to you that he wants the leftovers.
3) He always pulls on the lead when walking (always has done). We went from a lead to a harness about 18 months ago and the pulling improved momentarily but then went back to pulling shortly after. I have tried different methods, pulling him back saying "heel", having him on a short lead, a long lead and standing still as soon as he pulls but none of them have really helped. Maybe lead pulling is a completely separate issue to his aggression though ?
I've never really mastered this either
and have had to resort to a canny collar (halti type lead). It takes quite a while for the dog to get used to it, but it does give me a lot more control and the pulling has decreased dramatically.
4) On the subject of leftovers, treats - he has leftovers from us every now and again. Should we stop this completely ? He is not overweight but is it another thing we should cut out ? He has a treat every night when he goes to bed - this means that as soon as he comes in from garden, he patiently sits in his bed waiting for the treat before he settles down - is this a bad thing ? He will never ever do what you tell him to without a treat i.e. if I want him to get into his bed in the kitchen so that my daughter can play without him mooching around, he will stand and look at his bed as if to say "why would I want to do that ?". As soon as I go to the treat jar, he is in his bed like a shot waiting for his reward. He should be doing things like this without rewards though, right ?
My dogs sometime have leftovers too. It's not for everybody, but it's a personal choice. If my dogs have anything though, they have to wait until they are finished and it is always put into their bowls.
I think most people (certainly on COL) give their dog a treat at bedtime. Mine would be most put out if they didn't get their bedtime biccie
Vary the times you give your dog a treat. Vary the treats. Sometimes it could be a gravy bone, sometimes a toy. Sometimes it could be a favourite game, other times it could be a stroke or just a reassuring "good boy". Wait until he has completed the action before he gets the reward. When you tell him to go to bed, he has to be in it, before he gets any of the above. Once he gets used to the different rewards, then start leaving them out, gradually at the odd time. He will still perform the action because he won't know whether he will get a treat or not. A reward doesn't always have to mean a treat.
Have you tried clicker training with him? He sounds as if he would really respond to this, and it is very easy, effective and fun for owner and dog.
You sound like wonderful owners, that have come a long way with your dog. I applaud your on-going committment, I really do