So I'm not an overly experienced owner, I'm a newbie as well, so I'll answer the questions from my own experience.
1) I have read about dobermans personality's a lot online, and understand them as being a very loyal and loving dog (given they have the right training and care) but how are they with young children? If they are introduced to children from being a puppy will they be generally friendly towards them, or will the similar heights be threatening to the dog?
Socialization is definitely key here, but I have found, based on searching on this forum, that some dogs are better than others. It's probably more personal preference and temperament - like people, do they enjoy the noise? Do they enjoy the quick movement? The unpredictability?
With Murphy, he loves my little niece, he's very protective and loving with her. Mind you, she is only 4 and a half months old and he's seen her since day one. However, he does not like kids aged 4 and up. They make him a little skittish and clearly uncomfortable. It's probably that I did a poor job socializating him with children, but I really don't know anyone with kids.
2) In the UK its illegal to dock a dogs tail and to crop the dogs ears unless its a working dog, but are there any health benefits to the dog having these minor surgeries or is it purely cosmetical?
There are a few benefits. Less chance of ear infections, wagging tail hard and damaging/breaking it, hitting things with tail or getting hurt in a fight. However, this is a personal preference. Many dobermen are just as beautiful natural as they are cropped/docked. Amelia_ is a frequent DTer and has a beautiful natural doberman.
I personally believe it's cosmetic, but it is part of the standard in the U.S. (not Canada).
3) I like to shoot/hunt a lot, mainly rabbits, pigeons, pheasants, nothing large like deer, can a doberman be a good gundog? Not for hunting, but simply retrieving the kill. The dog will of course be rewarded with some of the fresh clean meat from the hunt.
I'm not experienced with this, I suppose it would take training. I think it could be done. You'll have to find a good breeder that will find the right match for you.
4) how are doberman with new dogs? I live right on the coast line so have lots of beach area and grass area to walk the dog, but there are a large number of dog walkers aswell as runners who use this land, would the doberman best be muzzled (which I would prefer not to do so that the dog is free to play with me) or would it get on fine with other dogs, assuming the other dog is not aggressive towards mine.
A good breeder should
have a well-tempered dog that won't have issues here, however it has a lot to do with socialization and how exposed they are to other dogs. Many dogs who are well socialized simply brush off another dog like it's nothing. Mind you, a puppy will be very curious, which is why you'll also need to train him on how to behave while on a walk.
5) are your doberman's "barkers" being that if the doorbell goes the dog barks constantly and tries to break down the door to see who it is, or can they be trained to simply stay where they are and not explore the door? Just given there original purpose for breeding them (as guard dogs designed to warn you of intruders) I am not sure if its built into there behavior.
Yes and no. He barks like mad, but if I say "all good" he's fine. Mind you, he's a puppy and still needs to be trained not to do so. It's built in. You'll need to train him to cool it a little.
6) are there any specific training courses you can recommend for training your doberman, ran by police etc, as there dogs seem to be very well trained.
You'd have to look into what's available to you in your area. What are you interested in? Nose work? Schutzhund? Agility? These are all beneficial and put the dog to good use. I'd see what was available to me and check it out before making any decisions.