Go CATS, great instructors and a well balanced schedule of three sittings with a groundschool for each. Also you save around £1000 on Bristol. Great experience with them so far, last exams coming up very soon. Has taken 16 months to complete the course, however I work full time and I am having to retake GNAV (73%) and POF (73%) all other exams passed first time. Without the retakes I would have taken 12 months.