Adria have operated twice weekly summer scheduled services to Ljubljana from Manchester for many many years already.
Fares not necessarily cheap however many seats taken up by Shearings coach crowd and the Blue Rinse brigade on holidays around Lake Bled.
Belgrade without the coast and the once cheap Australia connection no longer viable imo.
Zagreb see above . Croatia is all about the Adriatic.
As LHR-LAX points out both Seville and Florence likely by Vueling soon.
Give up on Russia for the foreseeable future - The Economy is sunk.
Further Eastern Europe well just Bucharest left of any value imo.
Manchester and the North West probably needs to resurrect some of the Southern France routes again as the economy continues to improve and as for Italy how's about Rimini and Brindisi both were popular some years ago before Italy priced itself out of the UK mass tourist markets.
As for Santiago De Compostela/Vigo something tells me these would perform better from Ryanair out of Liverpool among certain communities.
From Manchester with Vueling wouldn't they go to A Coruna if they operated into this region ?