Do not accept a refund for your original ticket (unless the replacement is cheaper)

I've booked on another airline and claimed from EasyJet, they paid no issues or argument.

That said, if EasyJet were smart they'd rebook you on Aegean, it's showing £61 for BSL-ATH-BUD tomorrow at 9am...just keep things simple and book the WizzAir nonstop for £233 + fees