Hi Raw Data
All I can say is I'm a Heathrow man not LCY. We dictate exact speeds and so the radius of turn shouldn't be a problem. Having said that, it is quite a legitimate tactic to deliberately turn base leg early and go through the centrline from one side so that you can also turn the guy from the otherside onto base without pointing them at each other. If that is the case you should be warned that you will be going through or at least that you will be going right up to the centrline before you get the turn in. A point of professionalism I guess. Maybe the LCY boys aren't doing that.
Some aircrft, most notably the A320 do seem to be slow in the turn if the auto pilot does it. We have queried this before and found that the auto pilot was only doing a rate half turn. It is quite a common practice at Heathrow to ask traffic turning downwind off BIG to do a manual turn.
Hope that helps.
