Me too, in fact I drove at 20 or under in Portsmouth long before they changed them all to 20 zones. It pisses people off behind me but I just don't feel comfortable going quicker, as I can't register all the gaps in cars quick enough where people could be hiding.
Going back to my previous, I also drive slowly because there are some real pillocks on the paths who don't seem to realise how dangerous it is just stepping out - especially at crossings it really winds me up how we have to obey the red lights yet they just walk out on the red man, right in front of my 2.5 tonne 4X4!!