[AndrewA]

By way of update - I gave up! Finding people to fold the metal is no problem but matching the etched aluminium is.
So then proceeded to make the best of what I've got.
I tried various polishes but they were too abrasive so I went with a tip from the internet by a chap who cleans up old aluminium signs/door plates.
Half a fresh lemon dipped in table salt and rub away, topping up with salt regularly and then wash off pulp/peel/salt with water at the finish. I think it has helped them get as good as they're going to get.
Will post a picture later so you can judge for yourselves.
Andrew