There have been separate penalties in different parts of the British isles since at least the middle Saxon period, and not because those different areas had different kings... Fines, penalities, and even what's illegal were all completely at odds depending on where you were born. For example in Kent in the 8th century, you could get off the charge of murder by paying the Bloodgeld of the dead man, whereas in Mercia they had an immutable tradition for trial by witness for the same crime... So, no surprise there. Furthermore, in case you hadn't noticed, Wales is not part of England. They are both parts of Britain, though.