I usually buy North Face or Berghaus waterproof jackets from Blacks' online - the RG1 North Face is about £59 IIRC.
In Sports Direct there are sometimes ones that are cheaper and IMHO better than the brands above.
During the Summer I saw a decent Karrimor one in there with a fleece for about £50.
If you want something that's a bit smarter and not an outdoor type then I bought a Jack+Jones coat from House and Fraser for about £80. Not sure if it's a good/trendy make but it's warm!
Edit: similar to this