Vueling carried 1,845 pax on their RNS-LGW route in April and this summer they are operating 3 x weekly. You would think it would dilute the SEN route somewhat but sometimes competition serves to make the route (RNS-LON) more visible and the market grows accordingly. Flybe's LCY-RNS didn't visibly harm the SEN route which showed good growth during last summer's peak holiday travel period. Overall yields may have suffered of course.
SEN-RNS has certainly performed better than I thought it would when Vueling came on the scene last autumn(?).