Are you allowed to take stuff from council run electronic disposal sites? (in england)?

Not generally. It gets recycled and the components and materials are sold, so you can't take it for nothing.

There is also the health and safety issue. Councils do not want people poking in piles of old electronic equipment in case they get injured in the process and try to sue.

No. They look on it as stealing....which is stupid as you are supposed to support primary RE-USE before recycling.

It used to work very well and you could take anything if you could make use of it - and save landfill, but now they sell it for profit.

That is why I have stopped doing it - and use freegle and gumtree instead.