if you think your M574 (let say US 9) is good fit, then you just order the same size for M576 UK.
but for another way, if you think your M574 is too roomy already,
then i think you shall order UK M576 at US 8.5.
for my personal point of view, if your M574 size is in between US 7.5 - 10.5,
basically that'd be the same for all M576 UK.
uum...... i think M576 UK is just a very little bigger than M574, so, go get the same size.
************************
about width. FYI.
UK 576 only provides D width, and that's very similar to all M574's 2E width.
so feel comfortable to order that 576's D width. for sure.
nbfans ^_^ Love/Hate