I had my Octavia VRS done by FAT Dubbers who are behind FWB on the Minera industrial estate and it transformed my car. They use the Black Code system, I chose these based on their reputation and guarantees. They offer a 14 day money back guarantee if you aren’t happy with the upgrade, they offer a 12 months parts guarantee so if the upgrade damages anything, they will repair it and also a lifetime reprogram should the ECU need re-flashing by a main dealer.
Oh and I don’t work for them I was just impressed with the service :)
Take a look at https://www.facebook.com/FatDubbers