I don't see what is dishonest about Cameron saying he wants to try to get a better deal from the EU, and from what I read, he's likely to get something from Merkel. If it is more cosmetic than real, than Cameron has a tough decision to make about which way to go on the EU referendum. He's party is deeply divided on the issue is my impression.
The dishonesty is in the fact that Cameron and the Tory party don't believe in Europe. Probably Cameron and a part of the British Euroesceptics fear adverse economic consequences if they depart, so they try to get the best advantages possible while they oppose any attempt of further European integration. For many people in the Continent, that's simply blackmailing. Don't you see a certain parallelism with the SNP? They would like to achieve the independence of Scotland, but as long as they don't get it they want to get the best deal possible: further devolution.
Did the SNP get many votes from those who voted "no" on Scottish independence? My impression is that they did not. And how many voted SNP because they felt Labour was not left enough, as opposed to it being mostly about the independence issue? Anyway, whatever the dynamic, I would be very surprised if Scotland is still part of the UK ten years hence.
That is a question that I'll leave for Brit posters. The fact is that SNP got 1/2 of the vote in Scotland and won a clear mandate. It's plausible that there's a wide range of motivations behind that overwhelming support. Correct me if I'm wrong, but my impression is that they didn't run a campaign focused on independence, but on the defence of Scottish interests in Westminster.