Wire brushed both front callipers when I swapped onto winters and its back again, purely cosmetic I know but is only way to cure it to paint them ?

You could paint them, the key is preparation. If they aren't really clean, the paint wont adhere properly.
And you need to keep paint/solvent away from the rubber seals/disc/pads.
The paint will tend to look a bit tired with time but it does make cleaning them a lot easier.
Apart from that, I don't know any other way other than a regular clean.
Personally, I wouldn't bother. Another member of the failed FL2 clutch/DMF club, twice.

I had the same problem, last week I did a caliper per day when I was off work, wire brushed the caliper and dremmel'd the nooks and crannies. Removed the caliper carrier and did those too. Coat of Kurust then five coats of smooth Hammerite in the bit of sunshine we had.
PIA to do, and so time consuming but it just looks so much better.

Allow half a day for each front caliper, a full day to get both the rears done and clean the inside of your wheels while you wait for the paint drying between coats.

Some people have just Toooo much time on their hands

20 odd years of having GTI's and vRS's and I'm loath to see unpainted calipers

Click image to enlarge