In reply to Bonkers Dog:
Three basic approaches:
1. Something cheap and light. My wife has a Marmot Precip which seems pretty good - good features and cut, very light and packable but not great breathability - less of a problem if you delegate the rucsack to your husband. Humph... I've seen them in Go outdoors for less than £40 recently so for your budget you can buy a Rab Vapour Rise too!
2. Just look out for any old Paclite jacket on sale. I bought a TNF flight paclite jacket for £70 and have seen Mountain Hardware Paclite jackets at a similar price, again in Go Outdoors. On reflection the TNF jacket hood is rubbish and the rear hem is far too short but it is quite light and has kept me dry(ish) in some appalling weather including the Ben in wet snow and driving rain. I've also been disappointed with Paclite breathability - the inside gets quite wet.
3. Splash the whole budget on your ideal jacket. If I had the excuse, I'd be looking at eVent jackets from Rab or Montane.
Whatever you do, make sure you try on a few different ones. The best reviewed jacket is no good if their assumptions on body shape don't suit you.