I actually got a response from the GLA with a link to a really handy website

do check out Planning Aid for London, there's stories and training and all sorts on there.

"Just to say, only some planning applications are referred to the Mayor, which is usually the stage where we may intervene. I don’t have the resources to take up every application referred to him, but please do share details when you can and I will look at the scheme. 

If you have not already done so you may wish to contact Planning Aid for London who offer free advice to local residents and community groups in planning cases too. http://www.planningaidforlondon.org.uk/ 

I'd also recommend getting in touch with your local councillors if you've not done so already, who are in a better place to support you at a local level and dealing with the council. "