Going to try a 203 mm rotor on the front from a 180 mm which has the caliper mounted directly onto the fork. Can’t see an adapter for a 180 direct mount to 203 online, will a 160-180 do the same job if I maybe add a washer or two?

Yes!

Don’t bodge your brakes with washers…

Shimano SM-MA-F203-P/PM or SM-MA90-F203P/P

si.shimano.com/php/download.php?file=pdf/um/SI-0146A-000-00-ENG.pdf

Hope’s H type mount should do the job for most calipers without the need for washers, but a washer on a 160-180/+20mm will work fine too, certainly better than Tillydog’s suggestion which spaces it out 10mm too far.

certainly better than Tillydog’s suggestion which spaces it out 10mm too far.

How does it do that? The tech doc for that adaptor says it’s for taking a 180mm mount to a 203mm one…

There’s always one ! 😀

Those are +23mm adapters, for 180–>203mm

+20mm adapters will almost certainly cause clearance issues between the caliper and the edge of the 203mm disc.

[ETA: +20, etc. refers to disc diameter, not caliper spacing]

Fox do one that is for a 180mm post mount to 203mm post mount.

My mistake, apologies all round 😳