curling up on my lilac

I know you're over the pond there,and you may have diseases and infections we don't here, but can you go out and check the plant thoroughly? Are there any brown areas in the leaves, any sign of cobwebby type material, and are the leaf edges rolled up on themselves? This might be lilac leaf miner if so.
Also check the stems for any signs of fungus, rot or damage, please.

yes, I am. I like the summer here but it's too short, less than 3 months.
I looked it last night, the leaves are dry and edges rooled up on themselves, the tips of the leaves are black. no brown areas so far. the stems look good,

Thanks.

Possibly lilac leaf miner then, though usually you can see brown areas in leaves - the larvae are laid there and they crawl up to the edges of the leaves and roll them inwards. Can't recommend a treatment because your chemicals will be different there and in reality, your best bet is to wait till leaf drop, remove all leaves and debris, then keep an eye out next year when it starts growing again, have a treatment to hand at the first sign of anything on the leaves.