I think you're
extremely unlikely to get shot down in a spam can. Most likely post-landing tea and biscuits if you annoy them, or some unexpected formation flight with a USN helicopter if you're persistently annoying. If you're dumb enough to ignore that kind of warning sign then things may turn out really quite badly but you'd really have to work at it.
Don't know what the exact rules are. I know how a TFR bust works in the US (not from experience, I might add) but this is a bit more complex. If you really want to get yourself hurt by the US Navy, though, your best bet is to go into a pub in Portsmouth and start mouthing off.
