That is not new, NATS mentioned this the first time in February I believe
from the NATS careers facebook
currently, you will be able to apply from October, but from 1st April this will be changing and you will need ti wait 24 months in between applications. We are freezing recruitment from March but we can not at this stage say how long for.
That was in February, they also say the same day that it's due to eurocontrol guidelines.
The FAQ on their website reflect the same information
If I am not selected can I apply again?
Yes. You can have up to three attempts with a 24-month gap from the date at which you fail. If you are not selected, please do not be too disheartened – the selection process is tough. Because training is very expensive, we have to be very sure about our selection decisions.