I think this is what you are looking for:
http://re.jrc.ec.europa.eu/pvg_tools/en/tools.html#DRIt's a fabulous resource. Select your location on the map, select 'HOURLY DATA', select the year(s), slope and azimuth of the panel, select 'Radiation components' and click 'Download csv' to get hourly data for the whole period. The total insolation is the sum of the Bi (In-plane beam irradiance) and Di (In-plane diffuse irradiance) columns in W/m2. I'm not sure about Ri (Reflected irradiance) - probably also needs to be included in the total but it won't make much difference.
You can even upload your own horizon file to account for your own shading objects (but the tool does use geographical mapping data to calculate the horizon).
This a beta version of the tool - the current version is here:
http://re.jrc.ec.europa.eu/pvgis/ but doesn't directly give you hourly data for a specific year but does give average hourly radiation for a specified month. Its worth a look because it provides a bit more data. The monthly radiation tab also provides the number of heating degree days which the beta version doesn't seem to - but as it provides hourly temperature data for the year you can calculate that yourself.
[EDIT 1] Corrected DAILY DATA to HOURLY DATA
[EDIT 2] Attached 2016 insolation graph for East Midlands, south facing at 30% slope. This was derived from the hourly data and used the frequency() function in Excel. 4432 of the 8760 hours in the year received no insolation.
In 845 hours the insolation was between 0 and 5% of the peak, ie. 0 < insolation <= 53.6 W/m^2