I got a very waterproof, reasonably breathable and very lightweight jacket from Minx Girl - it's a Showers Pass (American company - Oregan I seem to recall, so they probably know a bit about bad weather) model in bright (but not dayglo) orange with plenty of reflective stuff, pit zips and a vented back. It was on sale at about £60. I didn't have huge expectations at this price but it's been an absolute winner that I've used (really used, not just taken along for the ride) on all my Audaxes this year (>10, 200-600km). Given that some Audaxes have been ridden in almost uninterrupted rain, you get the picture.
While it's not as breathable as my Gore jacket, the pit zips make a lot of difference for riding in warmer conditions. The big downside (and possibly the reason it's not £150) is that it has no liner at all so you need to use it with long-sleeved jerseys or wear arm warmers to ensure that you don't get wet fabric clinging to sweaty skin. The other thing is that it's not a 'race cut' - my Gore jacket is cut so short and streamlined that it doesn't really fit over my normal jerseys which extend beyond the hem and thus just conduct water under the jacket. So if I'm going out on a cold wet day, I wear the Gore jacket with appropriate thermals rather than a jersey but it's not the sort of thing I'd take in case of bad weather. For that, the Showers Pass jacket is much better as it fits over anything I'm likely to be wearing.
I'd definitely recommend Showers Pass gear - it's very nicely made and well thought out with some nice features (soft cuff and neck material, waterproof zips), and excellent even at full price (ca. £75 IIRC*)
* Sadly, I just checked the website and the jacket is now £100 - weak pound against the dollar, perhaps - a pity.