Instead of going for a ride this morning, I did some more digging. I finished digging over the second bed, made a brick pathway running between the two beds (using bricks we've found in the garden over the years), transfered some more rabbit-poo goodness into the beds and put the two wooden ends to the first bed.
Each of the two beds if 2.2m by 1.2m, so we've got about 5.25 sq m of growing space in these two beds. The old bed is 2.3 sm m and the small patch outside the back door is about 1.5 sq m. So that's about 9 sq m of growing space in the back garden.
(I did make a quick trip to work and back this afternoon, for a massive 5 mile ride...)