Thank you very much to each of you who took the time and trouble to offer advice - I'm particularly reassured by Mike's comment that the colour will 'weather in' and , if it still doesn't look good, then I can try the painting option. I'm feeling a deal easier about the work now.
If you leave the copper it will go a pretty inconspicuous colour, but do implore your plumber to be bothered to use copper or brass clips.
99% would use white plastic, which look horrible.
Of that 99%, half would use cheap ones which don't stand UV so they'd fall off in a few years.
Suitable clips can be hard to buy, so I suggest you get them yourself.
Ask him what pipe size he's using. It may be 22mm, or hopefully 28mm.
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