Pls help! where can i buy epl tickets in advance?

i m planning to go to england for vacation on april and wanted to go n watch and manu vs ars match, i know if i registered as a member in the official manu website i can buy tickests there, but is there other ways i can secure tickets here in australia? r there any 'other websites i can go on to buy tickets, if yes, will i need to collect the ticket when i arrive england or do they offer posting the tickets to me? pls help