The first photo looks to be identical to the kit I bought.

Is there anything particularly special about the seals or would a universal o-ring kit from a motor factors (or even Halfrauds if they still sell such things) do?

On the modulator, assuming the bores are all okay, there's 7 o-rings in there, so I presume that fluid could get around ageing ones. From the initial bleeding problems I had, it looks like there's "high" and "low" pressure sections to the unit, so I assume dodgy rings could allow fluid to be diverted where it's not wanted.

This is purely from my experience, not factual knowledge, so could all be bullshit!

What I did notice though is that my brake light would take a while to go out and then it would flicker sometimes when braking - presume the pump was also operating on overtime, but I can't hear it from inside. Following the rebuild, the issue has gone away,

Smiler wrote:

Is there anything particularly special about the seals or would a universal o-ring kit from a motor factors (or even Halfrauds if they still sell such things) do?

I've read somewhere (was it on here?) to avoid the red seals as they were made of less durable material and poor fitment. One more reason not to go for general O-rings.
I'm very happy with a kit from 4x4airseals , they have different kits to suit your needs and planning what to do.
I bought this one, it is a all-in-one kit, I've only done the compressor yet though, the valveblock I will do next month.