I have a 17week old ridgeback puppy who is a delight (most of the time) he is doing really well with training, had him at puppy school and have now started ringcraft, this week for first ever time, never shown before so all new to me.
the problem im having is, his heelwork on the lead is really good when its me and him, trots along by my side, doesnt really pull, a joy! however, when he sees another dog he gets so excited that he pulls like a maniac, and half chokes himself. now i know its normal for him to get excited, but i find it very hard to get his attention again. he walks with other dogs every single day as i take him into work with me (vets) and even when walking alongside he pulls to get to them. its only on walks when its me and him that hes well behaved.
any tips on how to get him under control when he sees another dog and get his attention back?

As he will end up being a very big dog I would invest in a  Gentle leader (or your preference) head collar.  as you will have control of hi head it is easy to get his attention back on you by gently turning his head back to you, and will avoid him choking.

you will need to train him to accept it though as often they will try and rub it off against you or go on two legs truing to get it off with their font paws.

I would always use any Head collar in conjunction with a half check collar so that the lead is attached to both, just in case the head collar came off..

thank you. ive been looking these up online, and they look good, does anyone know if any petshops sell them or do i have to buy online?

You can get them from PAH and I think most pet shops will sell them. We took our dog with us to PAH to get ours to make sure we got the correct size for her.