The big left turn could be there to show that the roads goes to the left, rather than carrying on straight ahead. That wouldn't be unusual.
Not uncommon but it still means you have to turn left.
Prohibitory, as in you can't do this...if you can't turn right there, use that type of sign!
A positive message? So, you should really carry on to the left...but I'm not going to actually prohibit you from turning right.
It is the wrong sign for the intended message (or at least the message as interpreted by the Police officer).
I am more than happy to concede I am wrong, but I can't find anything to back up a different opinion in the highway code.
http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/index.htm
okay, edit:
http://www.direct.gov.uk/prod_consu.../@dg/@en/documents/digitalasset/dg_070642.pdf
Possibly wrong. I still think it's a stupid choice of signs.
"Signs with blue circles but no red border mostly give positive instruction."
Then for that sign it says "Turn left ahead". It does not say that you cannot turn right however....seems to be a bit vague: as if it is encouraging people to not turn right, but does not explicitly stop them.
I would still be tempted to fight the ticket (possibly contact the local rag to get a bit of support)...but I guess it depends on what the alternative punishment is if you are actually wrong.