according to this, things were in transition, as of the time of this printing:
http://www.ncmd.co.uk/law.html
But notice its couched in terms of "archaeological". So no doubt this is a "pressing question" sent up the line to govt. archie's there, for their princely review. I mean, sure, no different than the USA, where .... some federal level archie can try to cite ARPA to your questions, etc.... But perhaps modern stuff on the beach is not under their concern. Or private land with permission (like they do 99% of the time in England afterall)l, since that would be outside the scope of laws that deal with public land use.
For example: Look at all the "dire" sounding things, on that link, about Spain, doh! Yet as has been pointed out, detecting is going on there. So I bet it's just like any country that .... as long as you're not snooping around sensitive historic monuments, or going into archie's pits, and are using some common sense, well .......