Altocumulus I do believe!!
I found this on the Met Office website
Height of base: 2,000 - 18,000 ft
Latin: altum - height; cumulus - heap
Altocumulus are small mid-level layers or patches of clouds - called cloudlets - in the shape of rounded clumps. These are white or grey, and the sides away from the Sun are shaded. Mostly found in settled weather, altocumulus are usually composed of droplets, but may also contain ice crystals.
The presence of shading can help tell the difference between altocumulus and cirrocumulus. Cirrocumulus are white but altocumulus can be white or grey, and the sides will be shaded."
I've been a right little sky watcher these last few days - I have a crick in my neck from constantly looking skywards!