Agree on reusable wipes, but no need to buy the poncey specific kind. Cheap facecloths from IKEA do the job, and you can get a set of 12 for less than a fiver - could, anyway. For out and about I used to buy Waterwipes in bulk from Amazon or Ocado too. No chemicals at all, yet still disposable. Reading the ingredients on standard babywipes put me off using them when DS was a baby, so I agree it's worth it. If you combine with flannels then that reduces the cost. But you go through a LOT when changing a bad poo out and about, so it might be worth doubling that number.
Babies grow so fast, so I'd buy babygrows from Mothercare or a supermarket (when babies you want the kind that go over feet, NOT the footless, because the poppers are easier to do up). No need for outfits - DS never wore them as they sleep so much, and would you want to in jeans or dungarees? And a sling is all you need for a newborn unless you have serious SPD, or other mobility issues, so that's sorted too.
I'd buy second hand cashmere baby cardies from Ebay to go over the babygrows. Non-itchy and much warmer than anything else, but also not likely to overheat. Take a baby sheepskin - so useful and the exchange rate may mean even a locally produced one is cheaper here (check, though). Fleece hats for the slings are also handy.
I never bothered with vests for winter - a warm cardy and blankets were just as good and comfier for the baby than 2 of cotton, I think. What I would swear by are baby nighties - they call them bundlers - for nights. You can change the baby so much more easily when exhausted and sleep deprived and the baby isn't wailing because you're faffing with their legs. Don't buy them new, though; they show up on Ebay a lot, very cheaply. A snowsuit/teddy bear suit is good for a sling in winter - second hand off Ebay again, as they outgrow them so fast they'll be in as-new condition from all those gullible first time mums like I was buying shiny new for their PFB. Better environmentally to reuse, as well as cheaper.
NCT is expensive - you can buy muslins etc more cheaply elsewhere I think? But NCT sales are brilliant, if you look to see if one is local to you that might be a shortcut to quality items at a good price.
DS had really sensitive skin and we found NATY nappies far and away the best disposables, everything else gave him nappy rash. Cloth nappies did too, and it was only when we switched washing powder to Surcare for all his clothes that we realised what was causing his eczema, so we think washing powder was a major issue for nappies, now. Surcare you can order from the website at a massive discount over supermarkets, so I'd have some put in your container.
A bath thermometer is really handy - I was so tired I might not have checked with elbow; a floating one was easy peasy. Baby toothbrushes are cheaper here and so small you can bung in - they can start to teethe really surprisingly small. Baby nailclippers too. Calpol and Calbrufen are useful though be careful not to use as a first resort, as they're linked to asthma. But so good to have at hand when the baby is snuffly. Also Karvol drops for blocked tiny noses (drip on muslin in cot).
In all honesty you don't need much clobber for a small baby. Most people have piles of stuff they never use. The necessary clobber stage starts once they're more mobile and need toys, books, a wider range of clothes etc.