X-default in Hreflang for English speaking countries

Hi all, I have a website that I will be soon implementing hreflang tags on between the main site targeting UK and other English speaking countries and a subdomain targeting Irish visitors only.

My question is if it is correct for me to have a Hreflang tag that's en-gb and X-default that are both pointing to the same URL? And of course an en-ie tag pointing to the Irish subdomain.