Not all builders register with the NHBC, so there’s no guarantee you’ll have a Buildmark Certificate. If not, ask your builder why they haven’t registered with the NHBC. They may have legitimate reasons – perhaps they’re a small company and can’t afford the fees – but it’s a good idea to find out what the reasons are.
If you still want to go ahead and buy the house, you’ll need to take out your own buildings and contents insurance for your new build. Remember, you should buy buildings insurance from the date you exchange contracts.