Don't buy the BT jacket, it'll be a generic non breatheable, waterproof coat from a catalogue with a BT logo on it.
Do as has been said, and pop down to TK Maxx.
Loads of coats at half the price, and they have all sorts.
Look for - Breathable fabric, waterproof (splashproof if you're a pussy (N)), ideally with a low back section to cover your arse, reflectiveness for safety, taped seams, and non-mainstream brands.
I have a RLX coat (Ralph Lauren division that makes outdoorsy stuff) and it's pretty average, even though the price was very high.
Nike and Adidas being the exceptions, they make some very good, if over priced, kit.
Karrimoor, Peter Storm, Outdoor scene, Gul, Marlin, Fox all make very good coats.
You'll have to decide whether you want a windproof shell thats light and you can fold up into a tiny bag but isn't warm as such, or whether you want a proper coat that is bulky but is nicely padded and warm.
Remember the power of the fleece.
It appears i know too much about coats for my own good (Y)