This post is a long time coming, and probably one of our favourite and earliest modifications we made to Jeeves when we got him. That is... a front passengers seat. As you may or may not know, black cabs have a bit of a void in this area. We really wanted to be able to both sit in the front. Some of the important jobs for passengers include - getting the driver un-lost, being the DJ, holding the coffee and providing general entertainment.
We had seen a few different options around for the front seat, including a folding seat similar to the flip-down ones on the back. This would have been an OK option, but with a comfort factor of about 5... on the other hand, our friendly mechanics managed to install a drivers seat from another (dead) taxi into our space. There were some previous fairway models with a narrower drivers seat, and this was perfect as our passenger's seat.
If you have mega long legs, its not the most ideal of options, but given there is less space on the passengers side, we think this is a great solution and works perfectly for us. Apparently it is the seat belt that was actually a bit trickier to install, but our guys did an amazing job.
Here you can get an idea of the amount of space at the front, and the seat bolted firmly onto the floor.