It will almost certainly be something like Bilbao or Bordeaux, both good choices at around £218 return, with Barcelona (ex LGW), Alicante, Turin (much under-rated in my view) Geneva, Seville, Genoa, Jersey, Rome (ex LGW) a few quid more but typically below £230 return. Maybe worth cutting and pasting an ITA matrix query for recycling and then knocking them off as you go.

There are day trips available in ET to places like DUB, GVA, LIS and so on, POUGs are available to make for a cost effective CE option but it should not be cheaper than the above prices and needs you to book 3 or 4 days out.