Cracking job Colin. I did exactly the same as you, although the first time I polished them I used a 'proper' stainless cleaner, Solvol Bluing Remover, subsequently I've used Harpic, which is pretty much chemically identical and achieves the same result but at a fraction of the cost.
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I find the pipes start to bronze slightly after about 500 miles but, once you've polished them up the first time, it's easy to remove the discolouration with just a wipe over with a bit of Harpic on a sponge followed by clean water.