MarathonBet (has pretty much all matches in their offer), Betfair Exchange for bigger games and better odds, Bet365, Ladbrokes, Coral, BetVictor and many others.
Well above 20. Happens to have odds between 70 to over 100. Very important to place bets on best available odds.
Very long losing runs, sometimes days or even weeks without winners. Big winner can change the look of the whole month rapidly though.