I would disagree with the second answer: I'm self employed, and if there's one bit of advice I'd give anyone starting up, it's 'Aim High'.
You can NEVER set your sights too high or oversell yourself: Get together some samples, get them packaged nicely, print yourself up some bumf, hire a suit, meet with Sainsburys: They can only tell you to p*** off at the worst!
DON'T ask anyone else to join with you, if you have a dream, no-one else will ever be as passionate abut it as you are.
The best of luck.
ps Major Supermarket chains are very flexible with purchasing & WILL buy from small volume businesses regularly alongside their everyday stock.