Thanks, quisling.
I worked out the parsing a short while after posting – always the way! I had chosen the wrong vowel.
Now I'm not clear how to draw the lines "row by row", since we have established that there are only 5 unclued letters in across clues.
Designating them a to e, do I put a line thru a and b, then another thru b and c, etcetera?
After doing this there are already more than three areas!