OK, I've just watched the video. Now, Gaz, please don't shoot me but... I think you might be partially responsible. The gap, as you say, had only just formed however the side road had always been there, and the traffic was pushing forward and it is conceivable that one may form. The driver does not cross a solid white line, but enters the side road (admittedly across traffic). In that regard perhaps it is arguable that it is good practice to expect such a manoeuvre and should slow down in anticipation of needing to stop suddenly - this isn't the same as riding ultra-defensively to the point of making no progress, but similar to how one might expect car drivers to behave too.
HOWEVER. Do I think you are to blame? No. The ideas above apply equally to the driver - just because a gap has suddenly formed he should still move carefully forward in anticipation of traffic in the next lane, which indeed there was. As somebody else said, you could have been a bus and they still would have hit you. The major difference is you weren't exactly going like a bat out of hell, when a bus/taxi could have easily got the 30+ down there... and caused a MUCH more serious situation from the driver's point of view. The situation is most certainly not 50/50, but if it happened to me and I were in your situation, I would find it difficult to argue that the driver was 100% to blame.
I'm going to go hide for a bit now...