The £ would end up worthless. The only reason that they didn't do that to Greece was because they were in the Euro and that would mean Germany also being penalised by a devalued currency. So everything imported into the UK would be more expensive. Much more expensive.
Bring it on! I get paid in Euro from Dublin so in real terms I would have a big fat pay rise.
The spelling is sort of hit and miss, hither and yon. I prefer the British spelling, and so do MOST of the media. However certain words I do use the American spelling such as "realize", "jail", and "curb" to name three. The main thing is we do manage to communicate.
Realize and jail are perfectly acceptable in English. As for curb, it depends what you mean. If you mean to prevent or cut back, the curb is correct. If you mean the edge of the pavement (sidewalk) then it is kerb.
You really should be paying attention to your EU debt rather than engaging in frivolous conversations regarding the continental divide betwixt spelling:)