As you can see by the contrast in exposure between the lower half of the church and the upper half, I'd left the camera in auto exposure mode (not the done thing when intending to stitch images together). The camera has metered for the sky at the top of the church and underexposed the church itself. The bottom of the church is slightly overexposed as the camera had estimated a reasonable compromise exposure.
At first I stitched these images together using photoshop CS2; it took an hour of tweaking levels, warping, distorting and even cheating in cases where I thought It might go unnoticed. The image came out looking as though it had gone ten rounds with Mike Tyson; there were bits missing from it and even for a ruined church it looked battered.
Then along came photoshop CS3 and did all the work for me. Apart from a couple of minutes of tweaking there was nothing to do but admire how clever the new photo-merge capabilities are in CS3.