I’ve found the sports seats much more comfortable in the X1 and grand tourer, but both of mine have been cloth seats as I only went for the sports models. The xline can be ordered with sports seats at around £350ish. Like you I can’t have lumbar support as it presses on the wrong part of my back but I’ve found my seats comfortable enough, especially for my frequent European trips.
Sorry to read that you are in so much discomfort I hope you can get it sorted, line Josh says, speak to the genius they really know their stuff.