A friend mentioned to me the other day that HSBC now have a savings account in Australia that you can hold in a foreign currency. These types of accounts that I've investigated in the past have had quite high fees and little or no interest so really weren't meant for saving. I've done a little research on the account HSBC offer and the interest rate is extremely low, just .5%. But, the bank charges can be kept at nil if you keep within the rules - minimum average monthly balance of AUD 1,000 equivalent and no more than 10 withdrawals in a month.
I have contacted HSBC to ask if this account could be used on arrival in the UK and will update when I hear back. The other thing is that the account does not offer Visa or Mastercard access. Still... it's worth considering.