If your domain/DNS is with us, but your hosting is elsewhere, then you can likely edit your DNS records through your client area.
This has very basic DNS editing capability, you can also use http://access.enom.com which will allow you to edit dns record and whois details. You will need to request an access password for each of your domains. We can set the same password for all domains for convenience.
If you are getting your hosting directly through us, then you can login to the hosting control panel at http://wcp.zenmsp.uk/ to edit your DNS.
If in doubt please just contact us and we can make any required DNS changes for you, or can confirm where you can edit them yourself.