Yes filtering is legal and yes you have the same right to the road as anyone else I am not disputing that. But what is legal and right may not be sensible, in this case I think your filtering, in particular where you stop is not sensible.
Here's what I would've have done, indeed have done for many years, just so you have a fair chance to critique me as well. Filter as you did but when I found my gap move in to the left of the car in a secondary position as it's now called. Traffic moves off, as do you, at a brisk pace. On moving off if the traffic moves off faster than you the driver has the option of going around you - at this point you are trusting the drivers judgement but hey you are anyway. If it moves off at the same speed you stay ahead anyway and can make a gradual move back to primary 'if necessary'.
The difference: Well no.1 you are not 'invading his space' so you are more likely to be considered/tolerated, No.2 the traffic is moving slower, so if he does decide to go around you when he shouldn't, then everything is happening that bit slower as opposed to further down the road when it's all going a bit faster.
I also have to say, go further up the queue, no more than three cars back but probably one or two. The first two cars (in rush hour) normally move smartly away. The third and fourth tend to lag but after that everyone has seen the queue moving and they're all away quickly.
Key to all this is eye contact and reading the road. What's on the outside of the car who has to pass you, how much space does the driver have, how does he look etc...
Now I have to say I have not commuted in town traffic for over 10 years and things change, traffic has sped up, there's more cars on the road, people seem less patient but in my view that's even more reason to cycle sensibly.
The trouble is that drivers do not think you have an equal right to the road, so asserting it has to be done more subtly.
That's my view anyway, I'd better be prepared to defend it.
