The idea the whole time was to replace the pieces of board with larger, newer, cleaner cut board. But on removal of these panels, it became clear that the reveals were originally plastered, set back behind the architrave. This plaster was in very poor condition, so I set about removing it and exposing the red brick behind. It also exposed the window head, comprised of what can only be described as a giant piece of tree:
The window head appears to be a very crudely cut tree trunk, which is set rock solid in the wall. It's un-planed and rough to the touch.
The right hand window below. After the amount of effort removing the cracked wooden panel that covered the left window head, I decided to leave this one in place as it's undamaged and should sand nicely:
Once the wood and plaster had been removed from the windows, the reveals and under the windows was all plastered (the poor lighting makes it look rough, when in fact it's perfectly smooth):
Under the right hand window needed to be filled as so much lime mortar and small bits of rubble fell out when the plaster came off, it has yet to be plastered:
The bathroom reveals were also attended to, as the area where the reveals meet the window sides was cracked and disjointed due to the install. They are now perfectly smooth with a straight edge: