Parsley is different from most other herbs in that its best grown fresh every year, so treat it like a cabbage or lettuce and work a good bit of ground and plant it as part of your vegie garden or in big pots of rich compost. At the end of the year dig it all up, eat it all...and I mean all...roots and all and then grow some fresh every year.
We sourced some seeds from At the Garden Gate, see here. and for £2 you'd grow enough parsley to be self-sufficient in this glorious herb!