I have heard of fully qualified UK mechanics being given jobs by the main dealers but they insist they undergo intensive Spanish language courses. I dont think you will find a lot of jobs on the net because they will be advertised on Spanish sites or more probably in local Spanish papers.
In theCosta Blanca area there are some English owned garages - another option and I dont know the rates but they will be less than UK because cost of living is much lower - I use a main dealer for servicing and only pay around 16 pds per hour.