I'm no UK expert. However, 240 old pence equals 1 pound. 20 pence to one shilling, 12 shillings to one pound.
You might keep them as a conversation piece. The stores won't accept them, but I don't know about a bank. I once tried to use a 10 year old 5 pound note and the store asked me to exchange it with a new design note (the bank changed it)