Not a hard-and-fast rule, but I've noticed that the closer you are to London, London-Satellites (Brighton, Oxford and the like) or fake London (I'm looking at you, Melly - Saarf Lahndaahn my eye) the more likely you are to be a royalist; conversely, if you're in Manchester, Liverpool, further North or Scotland you're increasingly less likely to support the Royalty. You could say that the likelehood of support for the Monarchy is proportional to the distance from the centre of London.
Again, this is a slightly convulted equation - there's still families in Sheffield whose families' lives were made very difficult by William of Orange, and your average British Catholic is still bitter about the James II affair (and, obviously, that's to say nothing of the feelings of the Scottish, Irish, Welsh or Cornish).
Personally, the reason I'd support a referendum on the Monarchy is because I think the history of Britain is vicously entangled in not just the narrative of the Monarchy (I'd say Henry VIII or Victoria are as much part of the British folk-myth as Avalon, Gawain or Arthur are) but the narrative of the law of the land, proceeding from Roman occupation (or further back) through to parliamentary inteventions (your Georges, Victorias...). I know the Queen's position is, legally, pretty much a sinecure, but I believe that the alleged obselescence of a custom is not
enough to dismiss it outright (we still say 'bless you' when we sneeze, we still have knives to the right...).
Just to make absolutely clear - I'm not a monarchist, I'm a benign observer who happens to be British. And besides which, they simply don't
make celebrities like
Prince Philip. He's a bumbling posh buffoon with iffy views, but I'd definitely watch him if he had a chat show.