Where are you? We're in York. Can't really help you but I do support you and feel your pain!
DS2 is a bit quiet and immature (not in a silly, show off way, more in a not recognising he IS being snubbed way!) He's almost 8. An unfortunate class mix up at the start of this school year meant he was effectively separated from all the boys ALL of us would have regarded as his 'gang'! DS2 is quite unphased by it, but I have seen how his gang of erstwhile 'friends' have deepened their friendships (sitting together all day, same Beaver pack, same swimming teacher etc!) and how that gang doesn't include him any more. DS2 has never had a close friend which doesn't seem to bother him (though DS1, Y5 DOES tell me, 'Oh, DS2 spent lunch hour wandering around by himself' from time to time which breaks my heart...).
To be fair, DS2 is still on the party circuit, such as it is at 8, but not on the playdate 'roster' any more. I DO wince a bit when I'm standing with the parents waiting for the DSs to come out and it's all 'Oh, Mrs X, I'll pick up X after school tomorrow and give him tea then take him to Beavers if you'll pick up afterwards, OK?' and 'Here's Y's swimming kit from last night!' ALL the time! BUT I am aware that a) the boys' friendships are ALMOST enforced by the parents who are VERY close, b) that, knowing the parents separately I KNOW they have quite differing aspirations for their DSs come secondary!
Finally, we are about to move house, a short but school-altering distance. I admit I AM getting DS2 into the same Cub pack as these boys as DS2 wants that but I DO have an advantage there in that I am quite involved in Scouting thus will be there lots!