Gyratory traffic schemes, extended one - way systems etc

Very interesting (I live in these parts you mention). Is there somewhere to read more on the theory etc behind by why gyratories are dangerous for cyclists?

There's loads to read. :) It's not just a question of road danger; gyratories (and all one-way streets) also reduce cycling simply because of the inconvenience. In some ways, that's the bigger question. Crashes are a secondary outcome, a symptom, of that.

We put it under the heading of 'permeability': 'Maximum route choice, minimum diversion' for cyclists. 'Route choice' for short.

http://www.hackney-cyclists.org.uk/permproj.htm
http://www.hackney-cyclists.org.uk/permeability.htm
http://www.hackney-cyclists.org.uk/shoreditch.htm

(The Look Both Ways domain linked to in the above has expired, unfortunately.)

If you're interested in crash stats, they're easy to come by. Here's a recent Guardian article:

http://www.guardian.co.uk/environment/bike-blog/2011/jul/21/london-gyratories-cyclists

The Wikipedia article on roundabouts gives you some references:

http://en.wikipedia.org/wiki/Roundabout#Roundabouts_and_cyclists

There are still other problems with roundabouts, e.g. the long detour for pedestrians, the poor visibility across the junction, that you can't cross the street, the lack of activity in the centre of the junction, which is where the focus of interaction should be (all meaning that commercial activity never thrives around roundabouts), etc. It's just appalling urban realm design, all undertaken for the sake of a desperately stupid idea that modernity would mean that we'd all be driving everywhere in the future, since walking and cycling are bad and free energy would be neverending. Increased road danger is only a small part of the bigger picture, albeit of course the most immediately concerning one.

What campaign organisation are you part of?

The London Cycling Campaign (LCC), more specifically the LCC in Hackney.

http://www.lcc.org.uk/
http://www.hackney-cyclists.org.uk/

Where did the shoreditch one used to route you?

It was one-way clockwise, i.e. turn left at Hackney Road, go down Shoreditch High Street (four lanes of one-way motor traffic), turn right into Great Eastern Street, arrive at the Foundry junction after a long detour.