Just a reminder regarding Klarstein, the company themselves are no longer shipping to the UK as their couriers will longer ship here, so buying direct, and possibly sourcing parts down the line, is not going to happen for now. I have a Klarstein Brauheld Pro myself, bought direct, and believe me this is a concern to me. Any you see now are likely been sold by 3rd parties from held stock. You can see this for yourself if you visit the Klarstein uk website, a banner comes up.
As to the Grainfather, yeah looked into these when I was getting a machine, it was cheaper to get all the bits for a plate chiller, hop spider etc along with my machine, than it would have been to get a Grainfather. You can also buy counterflow chillers, but they're even more expensive, and seem to sell out fast.
I also tried the DIY route in the past, it cost more than my Brauheld Pro in the end, with more grief along the way.... Not worth it IMHO.