Right, had time to do some research today!
Made contact with Helix distributor in Germany, who put me in contact with the UK distributor, who was very helpful. They signposted me to one of their installers.
They previously tried the MK7 Helix kit in a MK8, and while it fitted, it didn’t work correctly. The centre speaker didn’t work, which is not only used for audio, but also SOS. The DSP/amp is locked down, so no way of tweaking.
A plug and play equivalent for the MK8 includes a Helix wheel well sub, an amp/DSP which can fit under the seat, and a harness. A power lead would also be required, and another lead extension to connect the centre speaker to the amp/dsp. So not quite plug and play. The DSP would then need to be set up/tuned.
This is all certainly dearer than a set of Focal speakers and a Focal amp, but knowing just how good the Helix with its DSP and still standard speakers was in the MK7, perhaps the Focal speaker would be a disappointment??
It seems someone tried replacing the Helix sub DSP/amp to one that could be tuned for a MK8, but it was expensive and still needs connecting back to the centre speaker.
Confused, particularly as they advised the processing/output on VW cars isn’t too good, hence the significant improvement adding a DSP such as the Helix. They suggested I could be disappointed with the amp and Focal speaker change!