Complex sentence: Until the fifteenth century, those who wished to attend university had to travel to England, to Oxford or Cambridge or the Continent, and just over a 1,000 have been identified as doing so between the twelfth century and 1410.
Split into simpler sentences: Until the fifteenth century, those who wished to attend university had to travel to England to the Oxford, the Cambridge or the Continent. Just over 1,000 students have been identified as doing so between the twelfth century and 1410.