Looks like Syringa vulgaris (Common Lilac). The seeds heads/fruits will split into two releasing two flat seeds.

Fractal, what you doing up this late? Phil J

Thank you very much.

Late or early? :-)

Is it worth saving the seed to propagate, or take cuttings?

You could try seed sown now or soon and left under cover outdoors in a cold frame. They need the winter chill to break dormancy and the cold frame will hopefully stop rodents eating them. They will of course be variable and not the same as the parent. Cuttings are very difficult and plants are normally either grafted or micropropagated (both normally out of reach of the layman).