Welcome to TAS
When you say 'registered', do you mean tagged or actually registered with a breed society? When you say the breeders were 'between Defra forms', do you mean that you had no movement document when you first got them?
For tagging - tags absolutely must be applied on the holding of birth, using their own flock/herd mark. The idea behind this is traceability and when you have a farm inspection there will be a problem if you have tagged them with your own herd mark but they have not been born on your holding. There may be nothing sinister about the fact that they haven't been tagged, but there is no excuse for it. It was probably that they had not bought in tags but as breeders they must have them.
You cannot obtain tags with
their flock/herd mark so you have to go back to them to supply them.
Tagging is a nuisance but it has a function in protecting all stock farms from disease, or rather enabling any disease outbreak to be traced quickly and minimising culling in the event that an outbreak does occur.
Similarly you must have a movement document for your animals as this is how movements are kept track of.
Please contact the breeders and ask for full documentation and tags.