If it's UK, it's most likely Transport Medium or Heavy.

Except it looks like FF Din to me.

Hmm... possible, as it looks like a council-sponsored sign. Still, I think it'd not be FF DIN then but a generic DIN1451. Of course, one would need a caliper or a micrometer to tell the difference.

That is an ideal road sign with illuminated letters that designers must taken into consideration. It's viewable in the public and effective for business advertising.