As a mature student (i.e. 21+) you can apply to do degree courses without any academic qualifications, although it would be helpful to do A Levels - and it is possible to bypass GCSEs and go on to do A Levels instead (or any equivalent).
You do, however, need to demonstrate that you are capable of studying at a higher level.
There is also the OU route.
As a mature student (i.e. when you hit 21) you can also go the Access course route.
My own experience is that I was accepted onto a degree course without any further academic qualification than GCSEs (oh and no English folks, due to it being coursework-based - I didn't do any coursework and was never entered, it's not ever been a handicap, I spent much of the time I should've been in school either in the library or in the pub reading .
I didn't go on to do it though, due to 'family circumstances' - although I am now studying again.
With regard to 'socialisation'. Both of my elder children were home-educated and then chose to go to school. At the first parents evening for the younger one the comment was, "You'd never guess he'd been home-educated, he's fitted in so well." LOL - I think people believe that home-educated children are sequestered away.
Of course there will always be a few families who lock themselves away, but this is not true for all of the HE-ers I know. My boys went through Beavers and Cubs, went to guitar lessons, swimming lessons and guess what - they also PLAYED with the other local kids (the ones that went to school).
I went to a meeting recently with the DfES and one of the local HE-ed teens was also present. When she mentioned her 'schooled friends' this was met with some surprise by the DfES rep (who was lovely btw) - but why shouldn't she have friends that go to school?
Children are children and friends are friends, regardless of whether they are HE-ed or not.