Having based all my calculations on the Billy dimensions from the ikea.ca site, I worked out the following configuration for the bookcase. 80-80-40-80-80. The top portion of the last 80 would be sacrificied as a false panel for the Electric Switchboard with the last shelf of the 40 unit being the incomer for the gas line.
Yesterday I pulled out the 3 Billy units that we had carried with us from Bahrain and which in their previous life held Lynda's shoes. I assembled one unit only to find that it was 60 cms. WTF????? A quick dash to Google reveals that this was from their now discontinued line. Inter-esting!!! Thankfully apart from the widths, the heights are all the same.
Anyways, rehash the entire project. The 40 unit becomes spare and I need to get myself to Ikea to grab the Billy unit that I saw in the AS-IS. I will now have the configuration 80-60-60-60-80 with doors only on the bottom parts of the 80 units.
C'est la vie!!
Lesson learned. Don't leave things up to chance. Constantly measure your Billy!!