@Lash,
Switzerland et. al. have never been members - talks about how they (now) are connection went over years, as well as those joining Schengen (Schengen is something, the UK never wanted).
They didn't reject membership: they never applied for it.
Britain has been an EU-member for 43 years. Now the voters said 'no' to it.
The EU wants it done fast.
The UK government not (“The period of informal negotiation prior to an article 50 process will be crucial and should not be rushed.”, cabinet minister Theresa Villiers, writing in the Observer,)
The crux is that not everything really is regulated article 50 - seems, the creators if didn't think that some country would leave.