Apex domains cannot have CNAME records.
Question and response
Question
dig servercity.co.uk. NS
Answer
servercity.co.uk. 5 NS authns1.coreix.net.
servercity.co.uk. 5 NS authns2.coreix.net.
servercity.co.uk. 5 NS authns3.coreix.net.
Authority
The response has no authority records.
Additional
authns1.coreix.net. 5 A 193.26.222.1
authns2.coreix.net. 5 A 83.142.24.1
authns3.coreix.net. 5 A 85.13.252.2
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0