I use most UK bookies, a lot of them don't offer many props or the full list of fights until nearer the event. the ones that do live betting are:
ladbrokes (again one of the best LB sites. have been quick to take lines down though recently in play)
williamhill (one of my favorite ones to live bet on, pre fight odds aren't as great)
bet365 (very quick to limit your stake)
boylesports (good for pre fight bets with good odds, LB can be good too)
unibet (usually have some lines up earlier than others)
paddypower (limited here too so don't use very often)
Betfair exchange ( this is peer to peer though not a bookie. hands down this needs to be the future of betting, I always try and get more people to use it)
other good ones for larger bets are (for me at least) but no in play odds
betvictor
betfred
matchbook( again, another exchange site, like betfair) great for last minute hedges on Moneyline)
sportingbet
stan james
and then there's the rest which are generally not as good for mma betting but sometimes have decent prices. sometimes they are more useful for accumulators than others.
corals (fairly decent all rounder for most sports, mma selection is limited)
betway (occasionally have 1 decent line, fairly rare though. also requires ID and proof of address to register)
bwin (again need ID for these)
skybet (I use these primarily for accumulators of heavy favourites, decent odds)
betsafe ( be careful as they put a rollover on EVERY deposit. would not recommend unless you see some amazing prices)