I often think Lisbon would be a good summer only route from BFS, a bit like NCE, were it ticks the city-break box, and with Estoril and Cascais down the coast, also the bucket and spade box. Plus Northern Irish folk seem to love anything from the Iberian Peninsula and Spanish Islands. Madrid also in that respect.
A previous poster had mentioned EZY to the Canaries. EI seem to do well on these routes, and prices seem far from unreasonable. While competition is generally good, I'd hate to see EZY enter that fairly established market now, when we already have competition in respect of EI vs the charters vs other sun destinations. Any fall in EI numbers to the canaries could really upset their aircraft utilization at Belfast, esp during the winter months when I would imagine these routes are the cash cows. I'd hate to see BFS down to one and a half based units, or just LHR with a based unit, and the rest W flights during the winter.