Domain change from .co.uk to .com

hi - 

My client wants to change their domain extension from .co.uk to .com (to appeal to a more global audience). The actual domain name will otherwise be unchanged, and the page slugs will also remain as they are now. Does anyone have experience making this change and whether or not it had an impact on traffic from organic search? I presume it will but not sure how much. Any insight would be fantastic. 

Also - Squarespace will automatically redirect traffic from the old to new domain, so I'm presuming there are no 301 redirects to set up in this case, but if anyone can confirm - that would be awesome.

Thanks!