Off to work now look forward to seeing how this progresses :) 

I strongly disagree Jeangenie my dog learnt most of his social skills on a lead, in puppy class all dogs were on a lead, when I introduce my dog to another dog its on a lead, I don't just through them together and hope for the best, just the other week a lady walking a doberman over the field when I was over there it came running over she shouted it back it didn't recall but stood still while she put the lead on it she asked if mine was friendly I replied yes both dogs met nose 2 nose with both leads tight just in case and both started playing the lady was suppressed and thought Akitas were vicious fighting dogs we both finished our walk together hers running free and mine on a long lead but playing along the way it was great, now when she sees me she still puts him on a lead to great us but then lets him off when all is well and that's the way it should be, people should not expect that other dogs are friendly, its up to the owner to be responsible for their own dogs control and dog walkers should respect that a field is full of nasty and nice dogs alike when I had a BC and a seen a dog on a lead anywhere I would put a lead on her its respect for others I didn't worry about what dog was like only that it was under control

well my staffie can be unpredictable with other dogs, but i wont stop walking her up the common because of it.
however, she is never offlead, but walked on an 8 metre retractable lead so that she can still have a run about.
IMO, if u have a dog that is dog aggressive or not aggressive for that matter and does not have a good recall when it sees another dog, then it shudnt be let off lead.  Its no good screaming its name across the field when u know its not gonna return. Even if ur dog is ok, the persons dog on lead might not be and ur dog could well get attacked.  I still dont understand why people allow their dogs offlead with a poor recall around other dogs.  Putting them on lead doesnt ruin their fun if u use a retractable lead.

Really sorry to hear this.  Been through very end of last year and you cannot be prepared for it at all.  Just watch out for his behaviour as time goes by and there maybe some psychological scars.