Thanks, that's a good suggestion to fuse the Anderson connection higher so I can use if for additional items. If I go do this route do you think 20 amp would be sufficent? In the wiring diagram I downloaded it details that the (20A-Cigarette Lighter U1, 12V Socket U5) are 20A.I was going to suggest an Anderson. The SB50 is a popular one and you should be able to find a fused loom one made up. It's also flexible as you could use it to connect a maintenance charger or solar charger while camping. If space is at a premium the smaller PowerPole series are also commonly used.
If you go that route you are likely to fuse the Anderson lead quite high, so consider you may need a smaller fuse to protect the fridge lead. There should be one in the 12v plug so if you remove that to change the connector you might want to think about how best to fuse it.
I've taken the passenger seat out today and I'm now able to get a proper look at the wiring. I know it might be neater to try and wire the feed from the reverse of the fuse box but I'm thinking it may be a lot easier to go from the top with a piggy back fuse? Can you also recommend what thickness of wire, would 2.5mm/12AWG be sufficient?
Also, I noticed that all the existing negative connections to the chassis have plastic insulated boots, is this something I need to get for the negative of my Anderson tail?