I am encouraged to hear that my room stats would still work if weather compensation is fitted, but I guess the question is whether adding a weather compensation kit would disable the OpenTherm control from the EPH stats. Here's the page from the EPH user guide for setting OpenTherm parameters:
View attachment 333559
And the climatic curves from the next page are:
View attachment 333560
Which go in a similar direction to the Ideal WC curves that
@MNW67 showed above (if you allow for the reversed axis).
If the Ideal WC Kit worked sensibly, i.e. took account of the OpenTherm information from the EPH stats, then it would be great. But if it's not sensible then it will override the OpenTherm values and I will have spent money unnecessarily. I guess I need to think of a question, but if anyone has experience of OpenTherm with the Ideal WC kit I'd welcome any input.