Well, as the only 2 existing UK routes are to London Gatwick & London Stansted, i would have thought another route to London city or London Heathrow, would only dilute what they already have. It certainly would not add any significant tourist numbers. RYR + EZY already operate in to Seville from Europe, so extending into UK should be achievable. However, maybe Monarch or Jet2 should give this overlooked city some consideration, for routes north of Watford. LPL or MAN + GLA or EDI, maybe seasonal Jan - May ?