yes
There are two types of aircrafts outside EASA, those on local permits and those that are on local CofA. The later will be aircrafts with a local certification, but not an EASA.....typically because they are old and rare. A number of ex military fall into this category. The aircraft in question is only built in 56 examples shortly after WW2.
I have noted a number of Yak18T's on Hungarian registry. I assume they operate under annex 2 in the UK?