hmm well I do act as a freelance consultant and designer mainly rather than "selling" solar thermal (I have been working in renewables for 10 years.) but I have no interest in driving to Oxfordshire to install or service if that is what you are getting at, I live in the Welsh borders : )

I think you are misinterpreting my comment - I am making the same point as you. It doesnt stack up financially, and that is the problem. If you are going to use solar thermal, 4msq of roof space will generate roughly 1500kWh per year, to achieve the same you would need around 16msq of PV panels (2kW). If the main aim of energy policy is to encourage low carbon energy production, solar thermal will do this at lower environmental cost, and still leave space on many people's roofs for PV systems to generate more energy, but at higher environmental cost. Thats really all I am saying, (alongside the fact that PV water heating is ultimately damaging if you are offsetting gas usage)

I'm not even denying that electricity is more useful - it is and I'm certainly not arguing otherwise

The fact is that around half the UKs domestic hot water use goes through the shower head, so if you like cold showers you are certainly in the minority, and I'm willing to bet you don't actually use water @ 10 degrees in your shower, but mix in at least some hot water. A very quick sum based on average UK consumption:

1 person showers daily @ 60litres per shower, source: http://www.waterwise.org.uk/news.php/11/showers-vs.-baths-facts-figures-and-misconceptions

thats about 30litres of water @ 60 degrees mixed with 30litres at 10 degrees to give a shower at about 40 degrees

30 x 5 showers a week (reasonable?) x 52 weeks a year x number of people in your household (lets say 3 as an average?) = 32,760 llitres of water heated to 60 degrees per annum, not allowing for bathing, washing clothes, dishwashing or anything else. If that doesnt represent a useful amount of energy to tackle using a small amount of roof space I don't know what does!

Solar thermal would roughly address that entire showering load for a family of 4 over the year, using 4msq of panels.