UKP is a series of datasets of UK regional precipitation, which incorporates the long-running England & Wales Precipitation [EWP] series beginning in 1766, the longest instrumental series of this kind in the world. The map below (fig 1) shows the regions that are available. The monthly EWP series goes back to 1766, whereas the monthly series for the sub-regions of England and Wales began in 1873. The monthly series for Scotland (and sub-regions) and Northern Ireland began in 1931. All the daily series began in 1931. UKP incorporates a selection of long-running rainfall stations to provide a homogeneity-adjusted series of areally averaged precipitation. The England and Wales [EWP] precipitation totals are based on daily weighted totals from a network of stations within each of five England and Wales regions. A full quality control is performed on the 5th of each subsequent month, allowing data from the most recent six months to be updated.

Info courtesy of the Met office