'Upgrading' to skinny tyres pointless for London commuting

Interesting thread.
An article by Frank Berto a few years back in Bicyle Quarterly suggests a 15% tyre deflection as being the ideal when riding (with whatever load) Along with that ensuring you have the correct tyre pressures front & rear taking into account the way you are loaded is fairly important too.
There is a tyre pressure calc here http://www.biketinker.com/2010/bike-resources/optimal-tire-pressure-for-bicycles/ that takes into account tyre size, total weight(rider/load & bike) & load distribution
it's a very handy tool to optimise your pressures and one that you can store all your bikes tyres on so you can make easy comparisons/adjustments taking into account varying loads etc.
As per the diagram below (& the excel sheet per the link) more load/mass is over the rear tyre (hence rear tyres wear faster) so running a wider tyre at the rear makes sense in any case.
According to the venerable Sheldon Brown & others having a wider front tyre gives you a little bit more shock absorbancy & a bit better traction into corners

I gave this a little try out this morning as I had to pump my tyres up anyway. I'd always been a 100psi man for training rides and 120psi for races, not for any particular reason just experience of what I like. It never occurred to me that different front and rear psi's might be worth trying.

At my weight (79kg, 90 with bike and kit) the calculator recommended about 120psi in the rear and about 90 in the front. Which is all on the huge assumption that my weight is distributed 60% over the rear wheel.

I can report that todays fast, spinny, fixed training ride in Essex was not only one of the most comfortable rides I've had on that route but the bike handled just a tiny bit better than it usually does and everything was blissful.