OK, this is a weird one.

I had the rear bumper and rear spoiler on the XKR painted.

The AM/FM antenna is a foil-type thing, on the inside of the plastic spoiler, spoiler is a urethane material, the antenna is a stick on thing on the inside, fitted from the factory.

The DAB antenna sit's behind the bumper cover, it's also a foil but on a plastic frame.

Both these antennas are mounted where they are mounted because they are behind plastic, not metal.

Since having the bumper and spoiler painted, AM, FM and DAB radio in the car has gone to shit.

I swapped out all the DAB components; receiver, antenna, antenna amplifier, antenna cable, results are the same.

Can't swap out the AM/FM antenna as it is stuck on the inside of the spoiler, but I still have the old spoiler with the original antenna in it, reception is fine with that one plugged in.

The only thing in common here is that they have just been painted.

Has anyone ever heard of this happening?