Hi Andrew,
Correction can be a thorney subject as converging verticals are often used by many photographers, including me! as a deliberate attempt to add interest and impact. However in this instance I personally would like to see them corrected as church interiors IMHO carry enough impact and interest already.
To correct them is a generally simple matter. In Elements for example, I use free transform to stretch the top of the image, and, if necessary compress the bottom. There are limits here as stretching the top too far causes serious image degradation.
I understand the latest version of Lightroom has an automated correction facility, although as a Ligtroom 4 user I have never used it. LR4 will do just as good a job even though it may take longer. Most editing programs can do it.
If you are serious about architecture, then a tilt and shift lens may be appealing to you, but they can be costly, but they allow correct in-camera.
Hope this helps.