Utter noob question: battery disconnect?

[khaito]

Noob question:
I've got two batteries under the driver seat on my van, the battery tray/box/thing is an utter mess and I want to take the whole thing out to clean it up a bit. What order do I disconnect the battery cables in? Do the main one first then the "aux" one? Does it matter? I think I've got the code for the radio so not worried about that (going to double check first though )

Also, similar battery question: I'll be hooking my van batteries up to a CTEK solar charge controller so they can be charged by solar and the leisure one can be charged by the alternator when driving. Do I hook the relevant cables up to the "aux" battery or the main one?

[scas]

is yours a mk6

[Brains_transit]

If your batteries linked together then it won't matter and I always do the earth cause if you do the live and the spanner hits the frame then it sparks which isn't good

[khaito]

is yours a mk6

Ya, sorry, forgot to add that. It's a 2003 mk6

[scas]

Then im guessing the batteries are just wired in parallel. So it wont matter which you disconnect. But as above earth first

[khaito]

Cheers, all. Was figuring negative first!