I found as many British pennies in my change as I have British 20 pence coins. Neither are the exact size, shape, or weight as U.S. coins but they seem to get mixed in at a constant rate.
Here's the stats...
Type/Country: 1 Penny / Great Britain
Metal: Copper-Plated Steel
Value: $0.02 in VF (very-fine)
Do you have a coin from Great Britain and want to know its value? Leave a comment/question and I will do my best to find out the price and history for you.