The Lake District is the wettest part, with average annual totals exceeding 2,000 mm. However, all of East Anglia, much of the Midlands, eastern and north-eastern England, and parts of the south-east receive less than 700 mm a year.
On average around 300 - 650 mm per year.. But it's a very hard thing to judge and would therefore deem this, and most things unreliable, from the amount of monsoons around the south west of India