Long sleeved, thin white t-shirts

[Roundaboot]

With the weather starting to turn, I'm thinking about my autumn/winter wardrobe. My standard over the past few years, especially when WFH, is a wool jumper worn over a thin long sleeved t-shirt for warmth, and also so the wool isn't itchy next to my skin.
I've got a couple of t-shirts which are starting to look rather ratty (I think they are both older than DS who is starting sixth form in Sept...) and could do with replacing.

Back in the early 2000s everyone was layering everything and these thin t-shirts were fairly easy to pick up but these days, they seem to be thicker. I don't want to be too warm or bulky under a jumper.
Has anyone seen anything? Requirements are long sleeved, thin, 100% cotton, ideally tall fit as I'm long in the body and need something I can tuck in properly. My current t-shirts are white but actually colour doesn't matter if I'm layering.

M&S have long-sleeved thermal t-shirts (heatgen) in differing warmth levels. The lightest weight ones are very thin and brilliant for layering under jumpers. The medium ones would also be suitable for layering if you need extra warmth. I'm 5'9" and find them to be plenty long enough too. They're not particularly well labelled on the website but the lightweight ones come in packs of two for £25.

Uniqlo heattech long sleeevd tops are very thin but warm.

Amazon essentials do a decent long fitting tshirt as standard. I would describe them as decent quality cotton so you can't see the outline of a bra through them/ skin colour but might be too thick for what you had in mind if it is is just a base layer.

I'm also looking for the same to replace my several years old J crew pure cotton scoop necks. I want cotton or a silk cotton mix with a low neckline that won't show under a v neck jumper. I can't bear anything with lycra or synthetic heat tech materials.

I swear by these - https://www.marksandspencer.com/en-fr/supima®-cotton-blend-long-sleeve-vest/p/P60440377.html

Thin, stretchy, warm, and long enough for me because theyre mens.

How about half cotton half modal? I've got these and they tick all your other criteria
https://www.kettlewellcolours.co.uk/clothing/outfit-builders/all/hetta-tee?colourid=992
They are long but I would size up if you don't want them too tight.

Jigsaw do them. Also Arket which are a bit cheaper.

Thahks for all the suggestions! I think I really would like 100% cotton rather than a thermal type thing.
The Arket scoop neck top is winning so far!

https://rapanuiclothing.com/products/3-4-sleeve-top

Rapanui?

I too have a pathological hatred of manmade fibres, but weirdly I get on very well with the thin heatgen tops mentioned by @SwordBilledHummingbird They are very good for layering and wash well, plus I don't find I overheat in them despite them being called thermal (and me being menopausal so boiling all the time). My 100% cotton layering tops all went baggy or have a high neckline which annoys me. Scoop necks all the way! Good luck with your search and please report back as it's a perennial problem trying to find simple classics like this!

@domesticslattern I agree, they don't feel thermal at all.

I think Hush might still do some fitted scoop necks but they're a thicker material so might not be great if you're not wanting to add too much warmth.

I've just bought the M&S square neck t shirt. it's great - a 100 % cotton t shirt. I've sized up 1 size as it's slim fit but it's a lovely shape & probably a deep enough front to wear under v necks.

I recently got rid of my old primark ones and ordered 5 shades from Arket. They do thin and also thick long sleeve.

https://www.oasisfashion.com/product/misspap-soft-jersey-long-sleeve-slash-neck-top_bpp05113

Oh, that looks perfect! Thanks!