So ds likes his own company. I get that - I'm similar. In many ways its a good thing to be happy in your own skin and not needing to be constantly 'out there'....
He seems quite popular though despite his self sufficiency, and has received a number of invites to birthday parties etc (bit surprised they are still going on in Y8 but there you go) but generally does not want to attend. These are not whole class invites - its usually half a dozen to perhaps 10 boys invited so he isn't just being asked for politeness.
I am finding it difficult because I have to lie for him to spare feelings and invent reasons why he can't make it. I also wonder if I should be encouraging him to go along? Not only that but a couple of the boys who invited him were noticeably disappointed that he wasn't coming 
When asked he has said:
- Sure he likes the host but doesn't consider him a good friend. Just someone he knows and gets along with
- He isn't keen on some of the other boys invited along - he might describe them as nerdy or weird or immature (that makes him sound judgemental, but children generally are quite blunt about what they think about their peers, and he goes to a boys grammar so to be frank, there are some unusual and quirky characters). Whilst ds is fun and has a laugh, he does have an old head on young shoulders and is bemused by some of his peers - for example he was a bit 'meh' re one kid who was doing pelvic thrusts behind the back of the teachers
- He just wants to be at home with his family and do his own thing
I've asked if he is being bullied and he is emphatic that this isn't the case. I've probed and he has admitted to feeling awkward in larger groups and preferring a one on one...
He isn't a total recluse and plays football with two separate teams outside school (which include some of his school friends)
He has accepted invites to parties from his two close friends but turned down perhaps four of five other invites.
Do I leave him be? Is there a problem? Is this a bit odd? Thanks for reading this rather long post