Are you looking for the correct Namesevers for Fast Hosts? They can be hard to find!
There are two to choose from:
ns1.livedns.co.uk (IP: 220.127.116.11)
ns2.livedns.co.uk (IP: 18.104.22.168)
AND if your provider supports any additional nameservers you can select:
ns3.livedns.co.uk (IP: 22.214.171.124)
When dealing with Fast Hosts we use ns1.livedns.co.uk.