Corfu has substantial obstacles on 35 due to Corfu city being just at the end of the runway. The 757 and 767 had plenty of available performance so were able to use 35 and return to the UK without restrictions. The 737-200 was very restricted and if 35 had to be used a tech stop usually at Brindisi would be necessary to get home. 17 even with a slight tailwind gave much better performance and so was the preferred departure runway.