Don't know if it is still the case, but if you found a Colorado Beetle in the UK you used to have to report it to the police! Sort of "Public Enemy No. 1". In the 1950's I remember Police Stations and other similar places used to have an identification picture up on the wall so they could identify any found and no doubt at that time report to our then Ministry of Agriculture (Now DEFRA).
Wether we ever got many imported into Britain I don't know, as I have never heard any publicity about them for years.
However, since starting this post I have just done a Google search and it is still a notifiable pest in the UK and within the EU. See:-
http://www.defra.gov.uk/planth/pestnote/colorado.htm
There is also a link on the left of the above site to how many beetles were detected in the UK in 2004 to 2005, and where from.
DaveW