Asus Zenbook Flip 14" OLED Laptop UP5401ZA (Intel Core i5/16GB RAM/512GB M.2 NVMe)

Zenbooks are metal chassis (Vivobooks are plastic chassis). You're not blind, it's not on their site.

P goes up to 28W H goes up to 45W.
The more power it can use the faster it's going to be.
That's why an i5 H is faster than a i7 P.

The problem with the extra power is it will consume more battery life. If you look at gaming laptops they come with huge power bricks. This is because a battery alone won't give enough power to run the dedicated graphics card.

I got a laptop advertised on here in December with a 1260p i7. Laptop battery life was advertised about 8 hours. I got at best 6 and at worse 4.
The 4 was using the CPU all the time such as gaming or recording video.

Just be wary of battery life claims. I always look on notebookcheck for reviews as they are very detailed and give battery life per use. You will often see 12 hours cut down to 2 or less at full load. Which means full brightness and full CPU load. Yes that's a 10 hour difference for the same laptop just doing different tasks.

Link below is for AMD version of this laptop. Note that runtimes range from 8 hours 42 minutes at best and 2 hours 04 minutes at full load, a drastic difference.
AMD Review (edited)

it is yes

here is more info direct from manufacture website asus.com/uk/…ec/

16GB of LPDDR5 is fine though, you're unlikely to need to upgrade that. More of an issue on the 8GB systems.

Lenovo - second hand ThinkPad Yoga, 5th gen or 6th gen if you're lucky. Not with OLED though.

You ever seen a Ryzen 6000 one in the UK?

Honestly might be a better investment to buy new... All components have expiry dates and get more prone to failure with age, especially batteries.
Changing an ssd isn't too hard but if you get a shop to do it, seems you'd be paying about £110-120 for labour. Depends on how much you value it but, this would still be noticeably faster and better screen etc even for everyday tasks.