It's always been the case that if an individual puts money into a foreign currency bank account for purely domestic purposes any currency gains would not be taxable. If it was for investment purposes, then the currency gains would be taxable, at least until 6 April 2012.
As you will see from the page you discovered yourself, gains on foreign currency bank accounts are no longer taxable and nor are losses allowable against other gains. If any of the money in the foreign currency account is invested and later returned, any foreign currency gains made during the period of the investment will be taxable.
I hope this helps but let me know if you have any further questions.
That isn't what I was suggesting. My apologies.
If you moved £1,000 into a US dollar account for a year and then convert it back into Sterling a year later, the gain won't be taxable. If, however, when you open the US dollar account you invest in US shares, sell them a year later and make gains on the shares, the currency gain inherent in the shares (comparing the purchase price and exchange rate at the time of purchase with the sale price and exchange rate at the time of sale) will be taxable in addition to the gain on the simple movement in the share price.