Although April was BS for weather this year in Spain, I would still recommend going in the first two weeks of April.. June is already getting pretty hot. +20c is usually the best for Mallorca, which it usually is in the beginning of April. You might just get a bit cold on the descents. (I still get sweaty on the ascents however..).
Bike with Ryanair should be 60€. I've only gone to Mallorca from IRE/FIN, so in the beginning of April there really aren't any cheap hotel+flight deals. I think that from the UK though you should already be getting some good deals for April. I've always stayed near the airport (bus 21), therefore I recommend taking the bus to Can Pastilla and anything within the Palma EMT -area. Bus costs 3€ from/to the airport. This year I took 2x23kg bags + a bike! Bus was a bit stuffed but everyone got onboard! pic: https://dl.dropboxusercontent.com/u/109 ... 150805.jpg