We are doing this some of the time, and it's working great. Here's what I learned when I was researching it:

- between 4-6 weeks is the ideal time to introduce a bottle, because the baby has (theoretically) gotten good at breastfeeding by then (some won't have), but they are not yet so set in their ways that they won't take to a bottle. Note that it's really important that your baby be good at breastfeeding before you try a bottle. This is because the bottle is easier to get milk out of than the breast, and it requires a different jaw action to do it. So if you give the baby a bottle too often or too early, you risk them deciding that the breast is no good, and then you have a problem.

- you have to keep expressing to maintain your supply. I found I had to gradually build up the amount I could express at a time.

- you should choose the lowest flow teat you can find. This is because faster flow will be too much for a young baby anyway, and you want to make them work for their milk, to reduce the difference between the bottle and the breast.

We first gave DD a bottle of expressed milk at about 4 weeks, but only because she was (and is) a very good feeder. If we'd been having trouble with the breastfeeding I would have waited longer to try that. She took to the bottle easily. I've let DH give her all the bottle feeds, because we figure that will confuse her less than if I do it. Getting DH to give her a feed late at night was a lifesaver for me at first, but remember that most babies change their sleeping habits quite fast anyway. Now, at 8 weeks, DD Is sleeping for 5-6 hours overnight, and I am not so desperate for the sleep that I need DH to give her a bottle any more. So we are still doing it occasionally, when I have to go out, but not for the same reason.

I bought the Medela Swing Pump before DD arrived, and we are using Medela bottles. I find they work well, but I don't have any comparison with other brands, so can't comment. We have:

- one pump
- two bottles (one is 150ml, one is 250ml), but I've just ordered more bottles, because it seems that 150ml is a convenient size for me to pump into to store in the fridge).
- 3 small teats and one medium teat that we haven't used
- a box of special bags for storing braestmilk in the freezer, that won't leach nasty chemicals into it, and so forth. You can't reuse these, but since I don't plan to be freezing that much milk, I think they will last a long time, which is good because they are expensive.

Have to say, the breast pump is one of the more useful things I've bought. Great for relieving uncomfortable engorged breasts!

Hope that helps.