UKCP09: Gridded datasets of annual values. Growing degree days
The day-by-day sum of the mean number of degrees by which the air temperature is more than a value of 22 °C The day-by-day sum of the mean number of degrees by which the air temperature is more than a value of 5.5 °C.
The datasets have been created with financial support from the Department for Environment, Food and Rural Affairs (Defra) and they are being promoted by the UK Climate Impacts Programme (UKCIP) as part of the UK Climate Projections (UKCP09). http://ukclimateprojections.defra.gov.uk/content/view/12/689/.
To view this data you will have to register on the Met Office website, here: http://www.metoffice.gov.uk/research/climate/climate-monitoring/UKCP09/register