UKCP09: 5 km gridded data - monthly averages for the days of ground frost. The data set contains 12 files (one for each month for the 1961-1990 average period). The individual grids are named according to the following convention:
variablename_mmm_Average_Actual.txt where mmm is the month name (e.g. Jan).
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/climatechange/science/monitoring/ukcp09/gds_form.html.