seriously mate , it will take longer than 30 mins .
TAXI def best.....Allow 10 mins to clear amex , universityand get on A23 then another 30 mins !
Agree - more like 40-45 mins (with no traffic) especially as roadworks on M23 before Gatwick slowing things down a bit. Best option though - I probably wouldn't risk the trains if I had a plane to catch