The Royal Mint had a limit on who could design for the Olympics, but I don't know how seriously they took it. One guy was Taiwanese or something, they did say "resident", I was, at the time of design and entry, living in Austria, but I am British and was only in Austria for 8 months, and for some unknown reasons was in the UK when we have to go to the mint, but the Taiwanese guy wasn't.
It'd be interesting to see if there's a difference in designs for this one pound coin design. Maybe they get a lot of stuff that they think just lacks understanding, I don't know. A topic of Britishness for this design competition is extremely hard.
http://en.wikipedia.org/wiki/Symbols_of_the_United_Kingdom,_the_Channel_Islands_and_the_Isle_of_ManA great example here, national flowers, well England and Scotland have one, Wales and Northern Ireland have two. National animals, Northern Ireland doesn't have one. Coat of Arms, Northern Ireland doesn't have one. Motto, Northern Ireland doesn't have one. Anthems, England doesn't have one. Flags, Northern Ireland doesn't really have one, the one it uses internationally for sports and things like that is a flag that officially went out of service, and has protestant connotations, which is a massive problem.
Traditional dress, England doesn't have a traditional dress, there are some that exist still but they're not really promoted.
Also, the Royal Coat of Arms neglects Wales, and has England twice with the three lions, also it has a lion (England) and a unicorn (Scotland) holding the arms, but no Northern Ireland and no Wales. And the UK flag doesn't have welsh representation.
Any design has to try and get all four countries represented in a clear way.
Being a foreigner and not understanding this stuff, it could be immense. (I'm not saying this is a reason to stop them).
However it's also possible that a foreigner might have a better idea of what is British than a British person who is stuck in the mire that is all of this stuff. (maybe a tea cup with English muffins or something)