Bosch KGN34V00GB/10 – warm fridge?

I have the above Bosch fridge freezer and a fairly common problem it seems – the freezer seems fine but the fridge is reading 14c – tested with my wireless BBQ thermometers!

I have had a previous fault with the freezer that I fixed by taking apart and clearing ice and the blocked drain plug that caused the issue.

What I have done so far…

1) Checked drain pipe and plug – fine and clear
2) Taken the freezer section apart, tiny bit of ice chipped off but all clear with no ice.
3) Checked the fan assembly – again all clear and appears to work as can hear it when I hold the door shut button closed
4) Checked the seal – appears ok, slightly crushed at the top but the temp doesn’t change even when I had a probe wire poking out of the door!
5) checked the light goes off – it does
6) Taken the fridge vent at the back apart – all clear but I don’t know how to test the flap thing ( I was surprised to see its mechanical and not electrically controlled)
7) Checked the back of the fridge, all appears ok and gave it a clean – drip tray had some water in and again pipe not blocked.

At this stage I have pretty much exhausted what I think I can test so I am assuming I have a faulty part?

I was thinking of seal or the flap thing – with the pair coming in at £100 I don’t want to order them on a whim to see if they are the fault so would appreciate any help or direction!!

I am not engineer of such items, I used to fix computers and laptops so wiling to have a go at most things!!

Thanks in advance!

Andy