If you think Covid didn't make things easy. Think Brexit next. All of the continental Europeans probably are breaking their heads on how to get to the UK and back with Cadets and RIBs without having to pay duties and taxes.
The Dutch Cadet Class Association is happy with parents who did put in some effort to find out and share. 

Do note that the information is gathered with the best of intentions and knowledge. Read them as tips and please do verify and check against your countries rules and legislation.
travel_to_EC.pdf