I have a 2011 S Clubman and I'm looking to refresh/upgrade my suspension and wanted to be sure I'm on the right path. I just got a set of Bilstein B8 and H&R springs. Will be picking up a "Cup Kit/Coilover Installation Kit" from ecs tuning. This one My questions are: 1. Do I need that or is there a better one? 2. What bumpstop do you recommend with lowering springs. Don't really want to cut the stock ones. 3. Is there anything else I should be doing while I'm in there? This is a daily driver that my wife will be using sometimes so not looking to make it too stiff.

 

Save your money you don't need any additional kit to install your shocks and springs. You just reuse the upper spring perches and rubbers as it is very simple. You don't even need a spring compressor to take the old ones apart.
Take the money you save without buying those extra parts and get a rear sway bar as that is going to improve the handling more than the shocks or springs.
https://www.waymotorworks.com/wmw-rear-sway-bar.html

For bump stops you can just cut them, or we do offer our custom short ones
https://www.waymotorworks.com/bump-stops.html

 

You can reuse your old parts to install the struts, but having new parts in hand will make your life easier if anything is broken or needs to be replaced. The front upper strut mounts will most likely need to be replaced, as they have a large rubber bushing that can get hard or crack with age, and the bearings will also likely be worn.