To ask for a guide as to what's genuinely worth spending a bit more on?

[TattyOldbit]

My default setting is cheapest, but I also get that cheapest often costs more in the long run.

Quality dies not always mean cost.
I pay more heed to reviews now for white goods as I have found that Bosch is over priced and not as reliable as it was.
Yes to a good mattress and sofa.Carpets depends on your circumstances but always good underlay.Lined curtains,cost ore but saves in electricity in winter.

Shoes & boots (I like Aquatalia)
Insurance
Car tyres
Tools
Wine
Personally, I also spend more on clothes and cars too, but that's for snobbish reasons rather than practical ones.

I cheapskate on cleaning products and washing powers as the own brands usually work just as well.

I'm currently wearing an M&S black polo jumper that I bought back in the autumn, that is as yet bobbleless as is a chartreuse green one I bought at the same time. I don't remember either of them being expensive, but I do wash them with a woolwash liquid. Perhaps that makes the difference?

In which case perhaps woolwash (along with limescale tablets if you live in a hard water area) need to go on the things--worth-spending-money-on list.

Quality is definitely worth paying for but sadly these days you pay more for brand and marketing than you do quality.

I love M&S meat but only buy it when it’s reduced. I love Timberland shoes which are comfortable and durable. Good quality make up and perfume although I have found perfume oil dupes to be better than brands.

Expensive loo roll is too thick and contains some form of glue to stick the layers together. Waste of money and a recipe for down-below irritation and blocked loos. I use the mid-price own brand.

Expensive make-up: again you don't want it too cheap (foundation especially; you have limited colour ranges and lower quality finish at the bottom of the range) but the £££ ones are often highly scented and you pay for the name and fancy packaging.

For me it's not always the cost but what's, imo, the best. I will spend without blinking on the following,
Skin care
Eyeshadow
Hairdresser
Bedding
Duvet and pillows
Wine 🍷

I'm not bothered about clothes, shoes or bags.

Bin bags. Cheap ones are never ever a good idea. Ever.

I’d go the opposite way with loo roll, the expensive stuff gives me thrush, I get the supermarket own brand.

I think a good sofa is worth spending a lot of money on, but I spend a lot of time on mine

As others have said footwear, bras, coats.
Also jeans. I used to buy them on a monthly basic cheap, now I buy 1-2 pairs a year mid range.

Shoes, pillows, duvets, sheets, mattresses, clothes, food.