After my post last week, and many useful answers, I proceeded with skimming
the concrete ceiling, after removeing paint and rolling on coat of Bonding
solution.

I used Thistle multifinish, and am generally happy -ish with the results,
being my first internal plastering job, in warm weather.

However there are the odd givaway scratches and pits in the surface which
are more prominent now it has 'gone off' and I am happy to spend a bit more
time getting that super smooth finish.

One person on this group previously said that a thin skim using BG Easifill
(a product for the dry-lining industry) was a breeze since it went on smooth
and sanded off a lot quicker than either plaster or polyfilla. Put it on -
let it dry then sand - as long as you can stand the dust.

If anyone else has other suggestions, I would be very happy to read them - I
was planning on using a sharp trowel and polyfilla in the pitted areas, but
I know this can be a bugger to sand off if you overdo it.

Cheers