Mine is fitted as close to the battery buzz bar as I could with about a metre of 240v lead running to a dedicated, tagged RED PP on a cupboard in van, I kept everything as short as possible. (my power station is in the boot) mine is just being for laptop/power tool/camera battery charging so they can sit nearby..... its okay to run a 240v extention lead , keeping the 12v cable short as possible is the thing...................... hooking one up to the standard van 240v circuit is an electrician job that needs to be certified as if you stuff it, you can easily destroy your whole rig and/or yourself....... One has to remember that its not just the power points that are on the circuit, switch one thing wrong and zappo, you could be on 240 and inadvertantly flick the invertor on, can you imagine the sparks, smoke and flame show and I doubt the van RCD would even trip out............... An electricians job that one......... both need to be isolated from the other so neither can be operated together by mistake, only get one chance usually with what we once called green steam...
I did contemplate running a lead, under the van from battery box and into the kitchen through a cupboard and fitting a PP there for use but I didn't like the idea of a long lead running underneath even though it would be shielded....... so opted for the shorter lead, works well.... I don't get in trouble for having My Junk in someones work space.
A Note To All :
........................................... Never ever make up a lead that has 2 x 3 pin male plugs fitted.,
........................................... When cutting a lead off an old appliance cut as close to the plug as possible and bin the plug .
........................................... Never have an extension lead with only one plug fitted, a male and female or none at all ..
........................................... Lots of deaths because of the above, especially kids and backyarders.