Quite. Who does? It appears to me to be the case that there is such an absence of choice in British politics that people are turning to nationalist ideas to simply create some idea of an ideological difference between parties. The SNP has benefitted from that and differentiated itself from Labour, despite having ostensibly similar programmes. In England no one can really tell the difference between Tory, Labour and LibDem, so by making some big deal about national identity there is something to actually talk about, other than who will best manage the NHS.
Absolutely. I haven't been aware of any insults coming fown from Scotland about Cameron, the English etc, but loads going in the opposite direction; plenty on this very thread, for example.
Those attracted to ethnic/regional/national identities, those who feel comfortable with their identity politics, will simply find new identities to grouch about. Cue Cornish, Yorkshire, Cumbrian, East Anglian, Wessex and London regionalist politics.