The way I understand it - and I could be quite wrong - is that if you want to fly an ultralight with Hungarian registration, you need a Hungarian ultralight license.
Somebody please correct me if I'm mistaken.
I think there are 4 possibilities:
-) trailer it
-) hire a ferry pilot
-) use your EASA license to get a Hungarian ultralight license. Some organizations make it quite easy, others less. Ask the owner there if it is feasible or not.
-) buy the ultralight, have it registered in the UK and then go get it.
If you fly over the Czech Republic and need support, let me know.