We're moving our domain hosting to you. Do you have a record of our MX records?
We are Nominet members and can provide this service for you if you wish.
You can look up MX records with dig:
dig mx yourwebsite.co.uk +short
10 mailin.phonecoop.coop. 20 smtp.phonecoop.coop. 50 smtp2.phonecoop.coop.
And there is a web interface that you can use here (follow this link, then insert your own website where it says "yourwebsite.co.uk", and click "Dig"):