I actually wouldn't stock up on nappies - I assumed I'd use Aldi ones, good price, well reviewed, and then friends gave us a 'new baby kit' present they put together with things they found useful and included a pack of pampers. She constantly had a dreadful rash from the Aldi, I tried the pampers one day and her bum was perfect. I did this at various points as we changed sizes - tried lidl, Aldi, Tesco - but no, her princess and the pea bum demanded pampers. Also water wipes. I honestly wasted more money with 'trialing' cheaper brands and stocking up in advance on things we couldn't use.
There's a huge variety in what particular babies need/want. We had a sicky one so needed about a million muslins. I know others who didn't have one. The next-to-me cot was the best thing we spent money on, we also got a Moses basket for downstairs from an Aldi baby event and both were great. I wavered about whether we'd need both but being able to have her more portable in the Moses basket was a godsend.
Be aware that Moses baskets/next-to-mes/ carry cots all need their own sheets and you'll want multiples. we only realised this when we set up the next to me the week I was due. Also if you buy them second hand, you still need new mattresses. Hand-me-down clothes are great, you can pick up equipment like baths v cheap too.
I wouldn't worry about a pump if you're feeding at the start, I would stock up on a few things like lansinoh cream as if you're in pain/discomfort you won't want to wait till morning or run to the shop. Thermometer essential, agree braun in-ear is great and v reassuring, car seat if you have a car, changing mat rather than table IMO as you can put it on the floor and just repurpose a chest of drawers for baby's clothes. We had a skip hop portable changing mat which seemed really expensive but was really well reviewed and was a great purchase, used until we potty trained a few months ago. Meant no need for a separate changing bag: we just popped it into whatever bag we were using at the time.