I think the really silly mega-bubbles outside London were in Bristol, Edinburgh, Brighton, Cambridge, Oxford and Aberdeen, Aberdeen has already popped (oil money on top of cheap debt followed by no more big oil money and no more cheap debt was like an Elephant gun to the city) I think the rest will now also burst in spectacular fashion.
I don't think Brighton can be described as a silly mega-bubble so much as a place where identifiable structural factors have led to slow and steady appreciation. Brighton changed significantly in character after it merged with Hove to acquire unitary authority (and then city) status, which is the best part of 30 years ago now. The high speed rail service that followed gave it the London-on-Sea identity that encouraged a considerable amount of corporate investment and relocation, ex-Londoners flooded in, and for the first time ever property values outstripped hitherto more desirable locations, like Lewes and the villages or the Wealden district. In the time since, what counts as central Brighton has expanded considerably, the housing stock has increased hugely, and yet both demand and prices continue to hold up.
I bought there in 1998 and doubled my money by selling in 2000, amid huge anxiety that the bubble would burst at any moment and we'd all be plunged back into the negative equity of a few years earlier. If I'd hung on to that property and sold it now, I'd be looking at about a 1500% profit.* That kind of steady appreciation is never going to burst now, because it was generated by factors that are longer-standing and less reversible than the conditions driving the recent property boom and current market slide.
I don't know the other cities well enough to say but personally I'd be cautious about hanging on for a mega-crash in any of them (Aberdeen excepted) without understanding more about the context surrounding what may superficially look like silly prices.
*See my forthcoming autobiography, Property Mistakes I Have Made, a tragedy in multiple volumes, featuring limited edition endpapers marinaded in real human tears.