I've also got the DCC50S and a Smart Lithium battery
I had planned on putting all the electrics on a kind of sled that would slide into bottom cupboard at the back of the van but seeing as you lot have made such a neat install under the drivers seat it seems a waste to not use the space!! I'll definitely be doing this also. I have got big enough solar extension leads to get to the front seat. It's just a case of mounting the fuse box in the kitchen somewhere and where to place the battery charger. I went for the Victron 12/15 IP65 charger with a little holder and plan on taking it out if I need it for another battery. I'll probably place a plug from the consumer unit just behind the drivers seat for the charger to plug in to.