In terms of expat numbers, Fuengirola and Benalmadena, along with Torremilinos, probably have the greatest numbers of Brits along the Costa del Sol. Other places in Spain with plenty of expats would include Benidorm/Javea on the Costa Blanca and Barcelona (in particular Salou).
In terms of finding jobs, I'd strongly suggest a couple of trips to the area you are going to move to to line up work (that means having a contract, etc. not just a vague word of mouth agreement). There are agencies who specialise in finding work for expats (wemploy.com is one I think) and estate agents and bars are typical employers that may not require Spanish.