I like your post but you are using terminology of banning of Bitcoin and other crypto currencies. In my view and given the technology used for these currencies as opposed to Fiat currencies, means it is next to impossible to stop without effecting other vital transactions some by banks themselves, that use the same medium ie Peer 2 Peer (p2p). Crypto currencies require no banks at all they can function with wallet(s) alone the only reason we need banks is so we are able to purchase goods and services with an alternate currency but only because the outlet does not support the crypto currency or vendor has no knowledge of it use.
Bitcoin and other crypto currencies bridge any border of any country, you can take some or all of your wealth with you, you don't even need to declare it when leaving your home or resident country to customs.
As such even if a ban was in place it could not stop the crypto currencies, well certainly not Bitcoin, in the fashion that funds for goods and services can be transaction-ed using a client wallet(s). They could stop people exchanging Bitcoins for Fiats or vice versa, but again as it stands at the moment and the huge profits that can be made on Bitcoin at least, reputable currency markets are already trading in Bitcoin and maybe other crypto's as well.
Summing up and in my unqualified opinion it is a bit early to tell but every time such a ban takes place or there's run of some sought on the banks people requesting their own money from there banks, the value of such crypto's just increase all the more. The over riding factor about Bitcoin in particular is that as a currency it is near impossible to fake transactions, it is after all a military-grade cryptography to secure transactions.
RE: What I Would Do If the British Government Banned Bitcoin...