uniq.com.au is fine, but that’s the domain that you have to add to the account. Only then can you host subdomains like jota.uniq.com.au on your account.
You can, but not directly. First, you’ll need to add the base domain (nuttyskitchen.co.uk ) to your account as an addon domain. Fortunately, you can do this by verifying it with a CNAME record, so you won’t have to change your nameservers or disrupt your other site.
How to add your domain with CNAME verification
Once that’s done, you can create the subdomain in your client area or control panel, then create a DNS record at Namecheap; specifically an “A” record with the same subdomain, that poin…