Can I combine Anycast OVH with Cloudflare

I can activate Anycast OVH in my domain registrator (OVH). Is good idea activate this option using the Cloudflare DNS?

That’s for DNS, https://www.ovh.co.uk/domains/dns-anycast/. If your nameservers are pointing to cloudflare, OVH DNS is not involved. I’d pass and save the £1.00.