Help me make this oretty

[RhubarbCrumble1]

The big border is being swamped with large bushes. When is the best time to cut these back? Any suggestions as to how I can improve this border? I've put many perreniels but they seem to die (erysium Bowles did well) as it gets a LOT of sun.

Usually the best time to prune shrubs is after they have flowered. Most shrubs then produce their next year's flowers on the growth after flowering.
But you could give them a light haircut now, or cut out a few branches and leave others.
How about putting in some spring bulbs to be going on with and then plan to put in sun loving plants next year. Cistus, roses, lavenders and all sorts from the daisy family would do well.
You might need to improve the soil, if the shrubs have been there a while.
Sounds like a fun project.

Thank you at JT05 I'll definitely start researching those for next year. Bought some good shears today so ready for pruning. The soil is good as we had rabbits roaming free for years and that border was their toilet! They ate everything that wasn't shrubby though leaving me with this

I'd be a bit cautious using shears. I prefer to use pruners for cutting smaller shrubs, they are easier to control.