try amazon and aliexpress. buy the pi zero with the pre soldered headers:

https://www.raspberrypi.com/news/zero-wh/

once you have the pre soldered headers it is easy to assemble. do not try to get the one without the headers unless you know how to solder microelectronics.

the site gives you all suppliers in the uk

compare prices.

the waveshare display is also available from all mentioned suppliers. aliexpress is reliable. they deliver to the uk. you can even pay with paypal and you are protected in case it gets lost or if it is defective. your card adds another layer of protection.

last but not least you need the camera. it is cheap. i got it from aliexpress for 8 bucks.

buy the open enclosure in the uk:

https://diynodes.com/product/seedsigner-3d-printed-open-pill-case/

as far as i know there are many dealers in the uk for those parts. prices vary. compare. you need to put more efforts into it but it is cheaper than anything else and you get standard components without the need to trust anyone.