The frozen accounts could be that the constant activity triggers some kind of money laundering flag which the banks then investigate.
This is the most likely scenario, rather than some stealthy grand bankster conspiracy against Bitcoin (whose market cap is still less than what the banksters, VISA, MC, Paypal etc. process in about five minutes - LOL).
Anyway it seems to be a right PITA to get coins in UK.
A little bit, but there are some reputable traders on this forum for smaller trades, e.g. I have personal experience dealing with Alwaysmining, and from what I've seen, Pteppic looks good too. For larger volume, direct wires to Mt Gox's Japanese-based GBP account isn't
that bad, even though I know it doesn't feel wonderful paying exorbitant wire fees to the banksters.
It's not for everyone, but starting a mining operation is another way to break the regulatory shackles making it tougher to obtain
BTC than it ought to be.