Blitz are low quality but a recognised name in British martial arts. As such, they make the most money. In turn, they have the most money to invest in ventures they wish to sponsor. Cage Rage is a growing promotion and I guess they decide to get in at the ground floor so they have equal credibility in both TMA and MMA circles. Most of the people I train with at my kickboxing class use Blitz gear, shoes and clothing. I think their clothing is made to a decent standard but their pads and gloves leave a lot to be desired. The stitching on their gloves is really poor and the new oversixed plastic logo on the wrist wraps are a terrible idea. Their logo printing comes off quite easily and in fact I was sparring with someone about 6 weeks ago and we had to stop because part of the logo print fell off into his eye.
Are Blitz one of the biggest Uk companies manufacturing martial arts goods? Yes. Are they the best? I don't believe so. Bytomic's Immortal range is actually pretty decent though.