“I buy a new duvet every month as I can never decide what duvet cover to get.”
You buy white. There’s no decision to be made - except in respect to fabric and then it’s linen or cotton (always buy cotton in the best quality you can afford).
You don’t need a lot of money. This weekend go to ikea. One of their best sellers is a white duvet cover with matching pillow cases.
Ikea has cheap towels. Just buy four and at least two bath mats. You’ll also need to buy new hand towels for every bathroom with some extra for replacements.
You can even replace your duvet cover while you’re there.
Walk around the kitchen area and put everything you need and don’t have in your trolley.
I’m not from the UK but I looked online for the things you need on the UK site (and picked my preferences - not necessarily the cheapest or the most expensive):-
Chopping board
https://www.ikea.com/gb/en/p/skogsta-chopping-board-acacia-80305422/
Cheese grater
https://www.ikea.com/gb/en/p/idealisk-grater-stainless-steel-66916200/
(I would prefer to buy an expensive one from a kitchen place that has rubber on the bottom - but you need something now and toy can always upgrade after you realise how wonderful a cheese grater is).
Tea Towels
https://www.ikea.com/gb/en/p/mariatheres-tea-towel-grey-80479592/
White bath towels
https://www.ikea.com/gb/en/p/fredriksjoen-bath-towel-white-00496717/
White hand towels & bath towels - set
https://www.ikea.com/gb/en/p/vagsjoen-hand-bath-towels-set-l-s29506004/
Bath mat
https://www.ikea.com/gb/en/p/fintsen-bath-mat-white-90443705/
(These are only £1.75 each!!)
Cheap white duvet cover and pillow cases
https://www.ikea.com/gb/en/p/dvala-duvet-cover-and-2-pillowcases-white-90377965/#content
(Only £25!!)
White duvet cover & pillow cases
https://www.ikea.com/gb/en/p/nattjasmin-duvet-cover-and-2-pillowcases-white-30337166/#content
(These are £65 for what I think is king size)
You can buy a good quality mattress and bed from a furniture store - you might have missed the end of financial year sales but many places are having mid year sales right now.
You can buy your sofa from the same furniture store or somewhere nearby. You don’t have to travel far. Take your time to buy the rug for it if it’s too difficult to make your mind up immediately.
I’m very much like you but in respect to clothes. It makes zero sense why I am constantly washing and running out of underwear and socks.
I haven’t always been like this. But it makes no sense as my partner earns very well and have access to money.
I also found it difficult buying a new bed for my child as it wasn’t just the bed - it was the mattress, multiple mattress protectors, pillows, sheets, multiple duvets and duvet covers. It seemed like so much I had to do because I had to go to multiple shops to get everything. I went to five different shops to buy things and even more before that while I was trying to find a suitable bed. I found it it just so much I had to do and so much driving.