They seem few and far between now that will take on "small" jobs. After a lot of searching I've found a place in Southampton that are a good bunch. Will find the details if you don't find anyone closer.
Yep I gave that a go as well. A kit from gateros. Took a lot of attempts to get the settings right - lucky I had lots of spare bits to plate! It came out ok, but I couldn't get the gold passivator to stick properly (this is quite common apparently). As this is the finish I specifically wanted, I ended up going to a proper place. But if you just wanted to prevent corrosion and were happy with a silver-ish finish, the kits are a good thing to play with.
Word of advice....when you are done with the kit DO NOT reach across your bench to pick up something and knock the bucket of chemicals over and have the liquid run all over your bench, down onto the shelf below, and all over the floor. You will be finding rusted out items for the next 10 years....
i could be way out here but something tells me that the yellow zinc plating is kind of gone off the market now altho i see the crowd in outofthefire's link state that they do yellow.
i do know there was something about it tho as if ye notice that many things that used to come with a yellow finish now come with a silver finish, ie hyd fittings, pins, bolts and so on.
perhaps it only affects industrial applications and not so much the smaller jobs.
John Street plating in Sheffield. They do 'blue' (silver really) or yellow (zinc passivation). It does help if you're local; I drop in and get bits and pieces done for ten/twenty quid cash. http://www.ukmetalfinishing.co.uk/
Here's my DIY kit results. Varying levels of quality! The pitted sleeve is one of the original bits, I was surprised how good it came up. As above, I ended up using a plating company but this was an interesting experiment.
Thanks for the replies. I have contacted the guy who will be doing the chroming and he says he can also do the zinc. DOH !! Don't know why I didn't think of that before !!