Wait, ESPN isn't an established channel in the UK? Yeah, Cage Rage and Cage Warriors certainly served their purpose. I think the UFC is pretty established if they have a UK president!
ESPN only recently bought out IRish based satellite channel Setanta which basically over spent in an attempt to compete with sky (owned by Murdoch who owns FOX in america) which is a long running and far more established company and Setanta ended up going bust as a result.
ESPN is as a result a very new channel in the UK although obviously being owned by Disney it has the money to be a more stable and long term competitor to sky.
(it can be view via SKY but requires an additional subscrition)
Put it this way, the number of UK house holds with Sky Sports packages dwarfs that of the households who have ESPN (although it is currently available free for views with Virgin media...the Richard Branson branded cable tv provider)
Yes the UFC has made great inroads here, it has a growing market share of the UK sport viewing market (probably on a par with other American sports like NBA and NFL) but it is still considered a niche market at this time.