From the PDF...
"There is no generally applicable offence of urinating in public. There was an attempt to insert an amendment into the Criminal and Justice Police Act 2001 to create a specific offence but the amendment was rejected...
However the offence is regulated by local bye-laws: Home Office Model Byelaws Bye-law No 24: no person shall urinate or defecate in any public place...
Although discretion not to charge might be exercised if a pregnant woman were caught short in public, it does seem unlikely that a police officer would offer his helmet for the purpose."
The 2006 Model Byelaw set 8 (Good rule and government) available at the Department for Communities and Local Government website has Urinating, etc. listed as Byelaw 13...
http://www.communitie...vernment/modelbyelaw6
If the local authority has enacted such a byelaw the maximum penalty allowed upon summary conviction is a fine not exceeding level 2 on the standard scale (£500).