The Boii were a tribe from what is now the Czech Republic that migrated to the British Isles and were/became the early Celts.
I think they settled on the Isle of Man... Boiis to Man, a favorite with teenage ladies of the time.
Despite both populations of England and Czechia were overran by several later invaders/settlers, there is still quite a lot of common genes between English and Czechs, traced to the ancient Boii.
The Boii were pushed partly to the west, to Gaul and merged with the Gaullosh tribes, but the bulk went east and were destroyed by the Dacians. There is not even a hint that they went to the british isles.
In fact the british isles were Celtic well before the Boii left Pannonia in the 190s AD.