The whole middle England boarding school thing is endemic in all private schools. After spending 6-12 years in such a protected and (usually) conservative environment, why would you immediately want to dive back into it upon acquisition of freedom? I don't understand my peers.
From my skimming of the thread it looks like you're very keen on going to the developing world and helping out, which sounds amazing, however I'll still contribute my idea.
Which is couchsurfing.
CouchSurfing - Participate in Creating a Better World, One Couch At A Time
You may already know about it, it's been called "facebook with a purpose", where you basically go sleep on randoms' couches, or beds, etc. I am buying my flights on Wednesday for a round-the-world trip where I'll spend a large chunk of my time doing exactly that. Me and friends did it in Sydney in October (I'm from tassie) and it was amazing, instead of waddling along the tourist track doing the tourist things with the other tourists you delve straight into local life. We got invited to a USYD house party and got told off amazing zine and art festivals and little bookshops and we cooked for them and played board games into the wee hours and shared stories and its so amazing.
Rant and a half.
Sleeping Around is suggested reading. About a guy who did a round the world trip Couchsurfing. Its V funny.