I never spent that much on clothes really. I am an advocate of cheap, cheerful and handed down:) I'm also one of those apparently horrible mums who prefers for small babies to wear babygrows and a cardi if needed (new territory for me as my other two were spring and summer babies) rather than 'proper' clothes' which saves quite a bit. A dozen of them, and similar numbers of vests with the odd outfit and hats and a snowsuit will see me through the first couple of months I suspect. For essentials, and after the initial outlay, I would say it is definitely easy enough to clothe a baby for no more than a tenner a month. Bear in mind that people will buy you epic amounts of clothes at first. Start training them now. If they want to shop - let them, just tell them that instead of just buying newborn, to buy a range of sizes:) If this goes to plan all you will need to buy will be vests and odds and ends if you are lucky.
Food, as seven says can be cheap as chips if you make your own, or hideously expensive if you prefer jars or eat highly spiced foods most of the time. I tended to just beat the shit out of blend what we were eating, before seasoning if it needed salt (rare!). I also loved those wee avent breast milk storage pots, as they were just the right size for a dry portion size of ready brek type porridge mix (I used Tesco own, it was about a pound for a huge box), which my son would eat morning noon and night. I always had one in my bag, as most coffee shops, cafes and friends were happy enough to provide a cup of warm milk - add stuff, stir and feed. Cheeeeeap and filling, and can be tarted up a lot with raisins, chopped aprocots and any other dried fruit that takes your fancy 
I tended to buy nappies on offer, and there is usually somewhere with the ones you want on offer. I never buy expensive wipes, for two reasons - they're so expensive for what they are, and I didn't like the smell of most, with the pink ones going so far as to trigger headaches. Supermarket own brands are just as good, and at one point I thought that the Aldi ones were the best about. Not had to buy them for a while so I have no idea what's what with them now though. I think I used to spend about twenty pounds a month, depending on the state of the digestive system.