In reply to PPP:
Depends on the season - winter - waterproof socks, overshoes, long bib tights. Proper chucking it down - Gore shakedry jacket - brilliant and in a different league to other jackets, including Gore. Neoprene gloves. Not chucking down so much - Stolen Goat Orkaan jersey and arm warmers - far better than the Castelli perfetto/gabba. The latter are too windproof and I overheat, plus they are not nearly as waterproof as the Stolen Goat stuff.
Spring-autumn - as above, but knee length bibs and toe covers to keep the worst spray out.
Summer - just regular bib shorts, toe covers if there's standing water. Maybe just thin arm warmers and windproof gilet if it's warm and not too wet. If not, one of the above as necessary. Windchill will soon cool you down if you're wet and riding any distance and it's throwing it down.