Another step closer today, finally got the breadboard ends on and dowelled. I used beech 8 mm dowels because thats what I had. Three at each end.
But I dont like dowels sticking through the top, it doesnt look right to me. So I drilled blind holes from underneath, tapped the dowels 5 mm below the surface, and used oak plugs to hide them. Thats gone pretty well.
I glued the middle 6" of the tongue and the central peg, but left the rest as a friction fit. The two side dowels on each end are in slots that will allow 5 mm movement in either direction, but the tongue does not break through the edge of the table.
I cramped the table up pretty tight before drilling for the dowels. Had to use 3 x 3 timbers screwed to my bench, with the wall as the back cramp and sliding wedges at the front.
The butt joints are not 100% though, Without gluing them I can see the join. But once the table is back in everyday use It should not be an issue.
I still have the two leaves to build, and then all the finishing, way more than I wanted to do, but needs must.