My 300A contoller's USB stopped working no warning at all. Maplin offered to upgrade me FOC to a new P4 if I wished. I didn't want to so they offered to swap out for a new controller. It was a 300C which I didnt want. They then found a 300B in another store for me. Just tried it out today. My longest flight ever. 14,000 feet distance totally standard no windsurfers or anything. Furthest I got with my old contoller was 11,000. I could have gone further but RTH kicked in. Maplin 300B doesn't have a CE sticker which is unusual - maybe that is why the range is better? Anyway very very happy now!!!