Gutted with insurance decision - any advice?

You’re being screwed, NIG can’t understand the situation as it’s clear that the other driver has “Failed to Give Way” the fact that you’re passing the traffic on the left is totally irrelevant. It is a straight forward Right of Way Violation. I don’t suppose the police were called?

Remember the Insurer doesn’t represent you… and based on my personal experience NIG are lazy! Tell them that it’s 100% not your fault and that if they settle you will take them to the Insurance Ombudsman.

Get it all in writing asap.

I had an accident whilst filtering traffic on the outside and a car pulled out of the minor road after being given way by the cars and I t-boned it. I thought for ages it might be 50/50 but at the end the driver was found at fault but think maybe that’s because I had one witness and the 3rd party had none. I wasn’t complaining as I do think the driver was at fault for not looking.