I use the same rain radar as Tim (Hamwich).
Plus Met Office charts like David.
Occasionally one other, which a pal of mine found the most accurate when he was Port Captain at the refinery in Pembrokeshire - Magic Seaweed (mainly for surfers but gives good weather charts and I know you said don't mention seaweed but if it was good enough for him...
).
Note that rainfall radar uses data from the air weather radar and can show rainfall which does not reach the ground.
Oh yes and Robbie's suggestion gets a
too - recommended in Outdoor Photography as being more accurate than the UK Met Office.
