http://blogs.telegraph.co.uk/technology/willardfoxton2/100012871/did-you-spot-this-budget-gives-hmrc-power-to-raid-your-bank-account-like-wonga/
1. HMRC can only touch FIAT bank accounts
2. to throw it on its head, if you only have under £5k in fiat.. sounds to me like they cant take your money.. hmmm tax free lifestyle if you only keep under £5k in a bank account.. ill keep my funds in bitcoin and only withdraw to fiat to top bank account back up to £4999.98
If you have less than £5k in fiat IOUs at the bank they can still confiscate those IOUs for taxes owed but they first have to go to the trouble of presenting their evidence to a court.