Good luck on your exciting journey, the first few days are quite hard but just remember after day 3 then things get much easier. One thing I would say it is not actually expensive if you weigh up (no pun inteneded) the fact that it comes out at 25 pounds a week for everything that you are putting into your mouth. I know that I would be spending more than that on my weekly food bill.
My biggest achievement is waking up every morning (ok, only on day 7) and thinking YEEESSSS one more successful day.
Go for it.
Julia