I've never seen a polished Spitfire. Polish yes, polished, no.
Must drive some of the purists crazy... "Looks like a bloody Mustang" they must be thinking...if not saying.

When the RAF deleted camouflage post war, they painted their aircraft silver...like the late Spitfire seen below.
More info on the decisions by IWM to "polish" their Spitfire.
Also, I don't remember where, but I'm pretty sure that Supermarine had a Spitfire on its company retainer that was either a very highly reflective silver or polished back during the post-war 1940s and 1950s and used for internal testing. They did it that way so it wasn't mistaken for a line aircraft, much as they did prototypes in Yellow.