S-o-T has a point

No they don't.
The bits of metal are as weak as anything I have ever met and they don't
work well. If you put a plastic number plate straight onto them, the first
tap smashes it. The original brackets were designed for the old metal number
plates. They work reasonably well with them but will still bend.
Most modern car plates are put on with double sided tape onto a large flat
area. That works far better and the plates are more difficult to steal.
That's becoming important with the increasing use of speed cameras. If
someone nicks your plates and is photographed speeding, you try proving
where you were at 2 am.

John

If your using nails make sure they are galvanised otherwise you will have
unsightly rust developing on the exposed parts.

They may be available from your BMW dealer but they will charge you an arm
and a leg.

Alternative parts can be sourced from

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=65584&id=11541

They also do an uprated heavy duty version suitable for the Booper S

http://www.screwfix.com/app/sfd/cat/pro.jsp?ts=65807&id=11036

Use Velcro