Don't confuse the IMC/VMC flight with being in cloud or clear of cloud.
They would have been in cloud until about 300' based on the met reports so by the time they were at 200' they should have been clear of cloud.
Did that make any difference to what they could see - even if they had been looking out (which I very much doubt for reasons previously mentioned)?
It was very dark, over the sea with a low cloudbase and no cultural lighting - that is IMC in anyone's book if you don't have NVG.
Is there anyone here that would cruise at 200 feet AGL while IMC for Ten Miles knowing there was any obstruction along the flight path?
yes, if it was necessary and the radar operator was up to the job.
It wasn't necessary to get so low so early in order to get to Blacksod - why they chose to do that is a big question and the answer is probably in SOPs and culture inherited from previous types.