After playing around with the keyboard, I noticed that hitting the Sym key, followed by the 'h' key brought up an abbreviated symbol pop-up for currencies. You may have known this, but this was new to me. So this is better than manually searching through the full symbols table.
But I noticed that the British pound symbol was third in the list - so you have to hit [Sym] [h] [h] [h] [Enter] instead of [Orange] [h] - 5 presses instead of 2.
I found a simple way of changing the order of the symbols - so that British pound comes first. This reduces the number of key presses to 3: [Sym] [h] [Enter]
I figure until someone figures out the actual keyboard mapping, this should be an improvement over the current situation.
This patch will only work for devices set to UK/English with the qwerty keyboard. I haven't tested this specific patch, but it did work for the US version. Use WebOS Quick Install to install it.