Don't be disheartened Catman - it can be a very long process and no news is good news
Some people wait months while some wait weeks; it's just the luck of the draw sometimes.
I had my interview last week and my references were checked a few days later so it has been relatively quick for me so far (I am waiting to hear back now too). I am expecting a long wait though (the recruiters did warn us this was possible). It's alright - I see it as an opportunity to work hard to save money between now and then as I know my wages will be reduced significantly during training if I make it through
I wonder if being progressed to medical and security checks means you're in if you pass them poppyseed? It wouldn't really make sense to put you forward for expensive medicals if they weren't sure to hire you or not! Good luck