For 240Z-style, you can buy replacement trim new that I suspect would be cheaper and far less hassle than getting originals replated. Not sure about 260/280/S31 style though. My own experience with replating plastic is that it is ineffective. The root problem is the old, dirty plastic substrate. Adhesion is variable. Might look good to start with, less so when it starts lifting off. That's when you can find somewhere willing to do it for private customers on a one-off basis, which is next to impossible.
Chrome paint finishes have progressed significantly in recent years and shouldn't be excluded as an option. Gloss black base, chrome tint, modern 2k lacquer. For UK light and heat conditions that should give a good finish if the base material is cleaned and prepared properly.