Not easily no. You can ban IP's from the "Server Administration" / "Admin Login" area of the control panel. You would need to get the non-UK IP ranges (inaccurate and difficult) and input them (long time).
From what we understand of the PPL having a few international listeners tune in shouldn't be a problem but as always we recommend contacting them to ask.
Also a few of our forum users might pop in an clarify this for you...