Buy to build to let – where to find land?

I am a semi experienced landlord with a few properties in London with some access to finance and potential to leverage in encumbered properties further. 

I am very interested in looking at buying land with existing planning permission or purchasing land with a chance of planning permission (appreciate these risks can be large).

Does anyone have any advice or experience on a small scale here (I’m thinking 3 dwellings or less to begin with)?

I have been in touch with a number of local councils, all of which claimed they had nothing for sale.  I keep an eye on Rightmove but nothing of interest crops up.

Has anyone got any advice/suggestions?

Given the lack of housing stock and political parties housing targets you would think there would be bodies set up and falling over thrmselves to help small scale landlords increase the level of housing stock?

Maybe I am missing something and the scale little old me offers doesn’t move their needle…

Thanks

Jerry