I wouldn't use silicone insulated cable for the loom Tom - one simple reason is that to get it tight, you'll need to wrap it.
Wrapping it means you will compromise the insulation, it's a lot more fragile than PVC insulation and the cost of silicone insulated cable would probably be prohibitive.
The Astra tailgate connector is a good idea and one i was going to suggest later once you'd got the lights working. They also have their problems but are much easier to work with to resolve.
There are other similar connectors that are more reliable, i'll have a look at what i can find.
