Advise please Hi Dano, It should have read 2 or 3! !
If you get good at the game then you will need multiple accounts, sometimes to get the best prices but often just to get a decent bet on. Until you get to that point then having 7 or 8 accounts isnt going to turn you into a great punter and having 2 or 3 with the big firms is safer than opening accounts with firms with little track record.
You will get best prices with Betfair exchange, but there is commission on top, and some markets just don't have the liquidity to accommodate your stake. In those situations having a bookmakers account is essential to get the bet on.
I think for a new recreational punter opening a Betfair and Bet365 account will be sufficient.