Regarding those underseat lights - they are not immediately visible - you'll need to raise the seat heights way up and forward towards the front to be able to get underneath to see what's there (don't forget if you switch engine on and hold the 'M' button down for 5 seconds, then let go and hold either button '1' or '2' down until you hear the bong, that will retain your current driver's seat positions, rear view mirror settings and air con temperature settings automatically. Just press the same button once to restore everything. Invaluable as it takes me ages to get my seat in a the perfect position and saves having to adjust it all again!
Here's the underside of the front seats - you can see (23) is the light - it is just protruding from the cable harness and cable tied to secure it! Accessible from the rear compartment as it is located nearer the rear of the front seat. Standard W5W like the rest of the interior lights.
- Front Under Seat Lighting
I think I had to snip the cable tie to release the light unit, change the bulb, then replaced the cable ties to secure it, otherwise it will dangle and get caught - so if going for it make sure you have some cable ties.