Hi Katy Halliday,

This is Jonis from Microsoft SharePoint Online Support.

I just reviewed your custom domain impressfingerprints.co.uk, and it is not active as your SharePoint Online for Office 365 public-facing website.  Also, your nameservers are pointing at ns1.secure.net.  The following link details how to setup the nameservers with your Domain registrar.  To review the article click on the link to Step 6: Move your custom domain.

It sounds like you were able to register and verify your custom domain in SharePoint Online for Office 365.  The last step is to change the address, to your custom domain.  To complete this process, from the Admin Overview page, select Management -> Domains -> Change address -> verified custom domain.  It is important to note that it can take up to 24 hours for that change to take effect.  It is recommended that you avoid editing your web site, during that

Period, as there will be times when your Website and Team site are unavailable due to website provisioning.  Because your team site is a sub site of your public-facing web site, it is affected by the change of address.

The changes to the nameservers and custom domain address are the last steps you need to take to set your custom domain as your SharePoint Online public-facing web site.  The following document details the change address process, to review the article click here.

If that did not answer your question or you still have a domain issue, please let me know as I will continue to monitor this thread for a few days and will reply to any additional posts or questions.