Regenerating garden shrubs

Lots of common garden shrubs can be regenerated by a hard prune back into bare stems.
Once the plants are pruned back into bare stems the additional sunlight activates dormant buds in the stems.
After pruning back feeding with a general feed such as Growmore and then when the new buds start to grow on the bare stems that have been left in the spring ( April ) start to feed once every two weeks with a high nitrate fertilizer such as Miricle-gro and keep the plant well watered.
In your case the buddleia near to the pergola at the rear of the garden can be cut back by two-thirds and the other plant Hypericum perforatum can also be pruned back to two thirds

When you cut back the buddleia you can take some hardwood cuttings