How they're being eaten sometimes gives a clue to the pest - things such as whether the leaves are full of holes, or notched by irregular or semi circular parts missing at the edges. The other possibility is slugs and snails, against which sprays would be completely ineffective.

Have you thought about wood pigeons? I have no real reason for suggesting this but a friend of mine has had her lilac bush stripped of all leaves by pigeons.

Thankyou both for your responses.
The leaves are eaten all over and end looking like lace. The flowers are nibbled before they have chance to open.

Shothole springs to mind, but you'd need to check whether there is a rather inconspicuous brown ring round the edge of each hole. The cause of this can be fungal or bacterial, so if you've had signs of powdery mildew too, its worth treating with a fungicide.
Otherwise, snails and slugs are still contenders, but also earwigs, particularly regarding the flower damage.

Thankyou for the advice

Look for a small banded snail, a stripey one. They can climb a long way, and eat about as much as I can in a day!

Thanks for that.
Someone suggested boiling onions and garlic and using the liquid as a spray. Apparently most pests hate it but not sure I want my little garden smelling of Garlic lol