I know, I know and I've calmed down now. I just felt so bloody awful when I got back from the school.
Ridiculous thing is I was delayed getting home because I was speaking to another mum about getting our two pups together for a socialisation session! 
We've been to the park three times today already. First time was just after I got back from the school and first attempt at both dogs on lead at the same time. It went really well, until Lurcherboy (who was ridiculously excited at having Pip out in the park with him) shot off after a tiny yorkie/chihuahua type pup on the other side of the park. I thought the park was empty, as I didn't see them come in whilst focussing on Pip's leadwork.
I didn't panic - after all, he always comes back .... well not today.
Little so and so shot across to it, fortunately realised it was a dog, circled it and came back to about my 4th call BUT THEN the little sod recalled, grabbed a treat from me, legged it and did it again!
He never does that, his recall is usually really good, at worst he'll head off, get halfway there then come back. If I'd had my wits about me I would have realised I had my whistle with me and I'm pretty sure he'd be back like a rocket for that, because he's been sharing Pip's recall training.
Fortunately the other dog had a very laid-back owner, who was on his phone with headphones in the whole time. I apologised and he said 'ah don't worry about it, he was only playing'. So at least I didn't have an irate owner to deal with, but I was seriously unimpressed with Lurcherboy nontheless.
Still, Pip got to meet a beautiful silky, long-coated lurcher and an adult cockerpoo, both of which were really lovely with him and was also fussed by several lovely dog-walkers and a couple of children.
Went back later and he met a really sweet border collie. He adamantly didn't want to meet her, but eventually came and sat next to me while I crouched down and let her say hello.
He wasn't as keen on the chocolate lab, so we just sat a distance away and I shovelled treats in his gob while he watched her calmly.
He's not at all sure about other dogs at the moment, in fact, he's stressed enough to not take chicken off me when they approach, but at least isn't reactive and doesn't bolt or panic, so all the signs are good.
Honestly, between him being ill, then the dcs being ill, then me being ill, all my plans for properly socialising him and getting him out and about loads were blown out of the water with us being cooped up in the house and now I'm back to blooming remedial training - which is always much harder than getting it right in the first place. That's what I'm p'd off about really I guess.
Trying to be less negative, I suppose he's fine with absolutely everything - except other dogs and being left, so at least I know what two areas I need to focus on.