Then learning about the glories of the ASCII table is long overdue. Hold down the ALT key, type in 156, let go of the ALT key... and bingo! A Pound sign: £. You don't NEED a £ key, as long as you've got an ALT key, numbers keys, and know what the ASCII code is for the character you want - and you don't even need to know that, if you Google "ASCII table" and print out what you find. Not just the £ symbol, but dozens of others besides.
WRONG: What keyboard you happen to have plugged in to the system makes absolutely NO difference. In fact, if you TELL your operating system that you've got a UK keyboard, then shift + 3 will give you a "£", regardless of whether the keyboard really is UK, US, German or Russian/cyrillic. I've been doing this as long as "IBM compatible" systems have been around, DOS ruled the world, and the function keys were found on the side of the keyboard, (rather than at the top as they are now.) But what OPERATING SYSTEM you've got might indeed make a difference.