Blue car is probably most at fault because he is overtaking and it is his responsibility to do so carefully.
Since you are in Blighty, the silver car could have hugged the crown better to make his maneuver more clear. It would be easy to interpret that he is waiting to pull out, rather than make the turn, because he is somewhat close to the curb. In fact he is far closer to the curb than to the crown of the road, where he should be. Here in America, no one understands road position, so there's no sense thinking like that :-(
Silver car should know to watch his mirrors.
Blue car should be aware of the intersection and approach silver car with caution. Silver car was moving to make the turn before Blue car came into the frame. Blue car doesn't appear to react until the last moment because I think he is assuming the Silver car is moving forward not turning.
Last comment: Blue car is overtaking in the face of oncoming traffic, so clearly he thought there was room to get past, suggesting my point about poor road position on behalf of the Silver car is contributory.
I'm pretty sure legally the Blue car gets the fault, though since I am no legal expert I suppose it's possible Silver car gets some blame for being a bad driver too.
I'd guess the driver is old and drives like a codger everywhere and should have stopped driving 5 years ago LOL. Which means you are the driver in the Blue car HAH.