As an airline pilot with a aerobatic instructors rating and 10 years of aerobatic flying under my belt I can tell you first of all UK airlines don't give a dam, in fact they probably would not know what an aerobatic rating is if it came through their letter box as most airline recruitment is now done by cabin crew on maternity leave or HR people who are more interested in your ability to be shafted by very poor working conditions roster/pay paying for training bla bla bla.
If I were chief pilot of Pizza Express Airlines I would send all my pilots on an aerobatic course! Its fantastic fun and great for flying confidence and general flying skills.
The most important thing is your instructor, chose a guy with a good reputation and proven track record in aerobatics. I would suggest you stay away from cesena aerobats and beagle pups they are just too under powered to be effective IMHO. look for something with at least 180HP as a min or you will spend all your time climbing. In order my ideal trainers would be Pitts S2A/Cap 10/firefly 180/200/260. You will get more done and have more fun 3 25 min pitts flights than 10 flights in something under powered with a crap roll rate. Just my thoughts others may have their own views.
Happy flying