Thanks everyone! Well, my new DA* 55mm arrived today.
I went with the 55 for all of the reasons mentioned above - and most particularly as I was shooting a wedding last weekend in the rain, and whilst my body (K5) is good to go, none of my lenses but the 18-55 kit lens that came on my K7 body is up to the task. I still have my trusty FA 50mm/1.7 which equates to 75mm on my current body, so a little less than the 55mm, and combined with the rest of my kit, gives me a pretty awesome coverage for most of my requirements as a people photographer.
In saying that, I am still going to get the 43mm - I am seriously holding out home for FF one of these days, so would like it in my kit for the precise reasons that Bing mentioned above.
I also picked up the DA 12-24mm/f4 today, so I am going to have a great play at this coming weekend's wedding! Can't wait.
tan.