Other answers are:

1) The can comes with a BS (British Standards) omolgation stamp and ref. number, this you will find it is not recognized nor understood by the spanish police, however no one that I know from the spanish forum that has bought cans from UK (formerly from Carbon Can Co.) has ever been prosecuted provided they weren't taking the piss with no baffles on and being stopped for extreme noise.

2) to the best of my knowledge there is no cat converter in aftermarket cans.