EHIC cover will continue because it's a European directive, not an EU one; in the same manner, if we were to be kicked out of Eurotran, the EU would have to take back the Nuclear waste that we are looking after for them. We are the foremost nuclear waste reprocessor, so they'll hang on to our expertise for as long as possible.
And I'll go with the loss of prosperity for a few years, but where does loss of sovereigntity come in to it.
Still, they're cute cartoons aren't they.