I've created this page for people pondering whether to upgrade their sidelights to LED or not, perhaps after having previous performed a HID upgrade.
I won't go into the explanation of how to do it because that is documented in the manual and for the S2 models is very dependent on whether you have;
1. An early S2 with H1/H7 headlamp cluster (inside wheel arch liner AND front lens removal required) or
2. A later S2 (inside wheel arch liner only removal)
The LED bulb I chose works for either type as the light emits from the tip of the bulb which is perfect for the horizontal orientation of the S2.
I cannot quite recall S1 fitment but if your sidelight relies on reflection of a chrome dish around it to project light forward then these are probably not right for you.
So this is the product I chose.