Late in the 2017 cruising season the permission given to check into the Loyalties at Lifou changed. The first brochure (see below) still says that this is permitted but in fact that is not so. This permission was cancelled due to a series of drug related problems with cruising boats. This situation may change again in 2018 so you may try out the following but don't be surprised if your email does not go through or your request is rejected.
1. Send an email with your request to douanes.nc@offratel.nc
2. Specify which island you want to stop at, give your boat name, POB, and onward intentions
3. You will get a reply. It may take more than one attempt. Their tel if you speak french is (687) 26 53 00 or 27 64 97
When you arrive visit the local gendarme and make sure you fly the yellow Q flag the whole time.
4. Then proceed onto Noumea, if New Cal is your destination.
Please note that you need to keep the authorities informed of any changes in your plans. This applies to all countries actually, and as long as they are informed you will normally find them accommodating. In particular New Caledonia officials are very familiar with the maritime world and what can change on route.

I checked the above email address and although I got a notice about it not going through, about 5 mins later I got a reply to say it was correct. I was also sent sent two attachments that cover this information. Received 6 Sept 2017. Yit Mike will put these on soon. It is in .pdf format and at this point I cannot add them. Done, thanks Mike.