Can any one point me in the right direction of a 180mm adapter for said caliper. I have got 180mm rotors and the caliper is IS mount but searching round the tinternet I can only find adapters that add another 20mm which is ok but I could do without forking out another £40 for a bigger floating rotor.

IS calliper and post fork, you’ll have to add 20mm.

You should be fine with 180mm rotors. This is what I had to use when I had a Magura Marta IS caliper on on a PM Bomber fork. You would not be able to put a 160mm disc on that setup but 180mm with that adapter will work fine.

you want one of these adaptors. I used it to fit a Hope XC 180mm IS mount brake to a set of post mount Rock Shox. No need to go up in disc size or anything.

Looks OK and works just fine. PS it looks pink on the website but it’s red.