Andymog 57 -- My Plus four was produced before the change to USB sockets so I have a lighter socket to which I can plug an adaptor with USB sockets for the sat nav etc.!!
Cheers!

I use one of these - image link

That's what I need!

I would have preferred a hella socket as I use hella to USB adaptors on my motorcycles and have them at hand. Nevertheless, 2 x USB sockets are also welcome, I use one to power my mobile telephone and use that in turn as a satnav.

Just noticed maximum output is 8W, whereas my compressor is rated at 18W.

Yes that lead appears to be trying to get blood put of a stone. USB sockets give nominally 5 volts in the 1 to 3 amp range. Give the loss in the voltage convertor you would be very lucky to get even the 8 watts mentioned.

If you don't have a cigar lighter socket and need a 12 volt up to 15 amp supply fit a Hella style socket and wire it in to a 15 -20 amp fused battery supply. Cigar lighter sockets are rubbish.

Me too - I've got one of these too - beats the wired up ones easily.

I have a Ford mini compressor kit with tyre goo for punctures, which I carry in the Plus 6. It uses the standard male type power connector that goes into a cigarette lighter socket. In order to get around the power needed I found on ebay a female connector with several metres of extension lead and crocodile clips on the other end. As a CX gen cars battery is easy access under the bonnet you can clip it to the battery terminals directly and still power a small 12v compressor. The only word of warning is to make sure the extension wiring is big enough for the power draw needed. The variants from China were too small a wire gauge, in the end I purchased one that was made in Germany, slightly more expensive but it was rated to handle the power draw.

Agreed. I had already thought that this is the only sensible option. I already have the necessary hardware and will make up a small fused harness which I will permanently connect to the battery.

Which I have now manufactured and fitted with interchangeable plugs so exchange between trickle charger and power for compressor is a few seconds work.
So, now all I have to do is find somewhere to stash the compressor, the jack, the can of goo, the spanner etc. Pity there is no quick and easy access to the cover over the spare wheel well. Plenty of space there!