Would'nt be without mine, have a helmet cam for bike which can also be used in ther car as a dash cam, possibly very handy in this compensation culture. Also have an old Sony cam corder for other stuff bike shows, air shows n such bit heavy n dated these days but a cracking picture.
Police cannot take the camera with out permission for a minor offense such as in this case road traffic Act. They would only be able to seize it if there was (deemed to be) a criminal offense then it would be classed as evidence so they could take it.
In regard to filming just be careful what you post and who has access to it. If you post yourself driving down local roads at silly speeds or doing something stupid then your gonna pay the price.
To be honest most biking films are boring unless it's like Stelvio, Nurburgring or the like anyway. I put of lots of runs over the years with out any issues despite spirited paces.
But as others say it can be a great bit of kit for things like SMIDSY's