Pruning advice, especially rhododendron, photo included.

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This lot is so overgrown there are probably plants we have yet to discover in here. Some is rhododendron, some other stuff. Also, the window almost completely in shade.

So how hard to prune and when? Should I leave it for now?

I don't want to lose all the buds that promise to look amazing in spring.

If you prune now you won't have flowers in the spring, best time is straight after flowering.

Thanks. I need to be patient!

I prune my Rhododendrons by taking out the very old branches down to the main stem. They are the ones with a tough, silvery woody look. This allows light to get in and new growth to emerge.
In an overgrown example I would take out about a third of the old stems. This means that the remaining stems will flower next year, while the new growth is developing. If you repeat the process next year, and the next, you will have eventually pruned the bush back to new growth.