When a vote is for 'status quo' or 'not status quo' then there'll be a lot of people voting for 'not status quo' that want radically different and incompatible things.
Realistically they should have planned more, but planning is limited when you're going into negotiations with an unpredictable third party. If other countries had voted to leave the EU, or the German or French elections had been different then the negotiation would be very different. Even the UK election after the vote could have wildly changed our brexit policy.
Presumably Norway isn't in the ECHR, which would be significant. Neither is it obligated to join the Eurozone. It's more complicated than you're painting it.
The ECHR is a separate institution to the EU anyway so I'm not sure why it would be relevant. Leaving the EU does not leave the ECHR, and there has been no referendum to suggest that the UK should do that.
None of this means that the recent referendum gave any mandate for leaving the ECHR.
Personally, I'm against referendums of any kind.