Airline takes in consideration just if you have done all the cpl/ir/mep at the same provider, because these are stage where you are actually taking the skills to become a professional pilot and the fact that you change for each rating a school, it could be a sign of not good progression in achieving your skills, because u change several time type of teaching and flight instructors during the most important phase of your training, but you can do the atpl theory and mcc anywhere you want, they don't care if u have done them at the same provider. The best modular uk flight schools are in bournemouth, which they are PAT (Professional Air Training) and BFCT (Bournemouth Flight Commercial Training) They also have got a good reputation flight schools such as multiflight, stapleford flight centre in london and Flying Time in shorenam. All of them have a good pass rate and top flight instructor with a lot of experience, but I always heard good rumors about PAT. People use to say that is the best modular school in uk.