I would say this is just scorching. Either frost or early morning dew sits on the leaves and is burnt off by the sun.

in addition to scorch I would also suggest possibly a leaf miner. in the areas that look lacy is there a small caterpillar munching away?

have you painted/sprayed a fence nearby and splashed the foliage? that could also be a cause.

Slug/snail damage is a possibility too, but if its planted in the ground and is relatively large (not a young plant) once it starts growing again it'll be fine, ivy's a tough old plant.

Thanks a lot everyone. Very pleased it’s not serious and should recover