If Converging verticals is another way of saying lens distortion, then yes, there's a system in Qimage for that.
Mike has built into Qimage, distortion correction for a number of cameras and lenses.
The best way is for you to contact Mike    mchaney@ddisoftware.com and tell him you would like lens correction.
He will reply telling you the shots he needs.
Then your correction will be inside Qimage, and automatically correct your lens distortion.
Fred

Thanks both;but Terry's right. It's just as I feared and it leaves me with two choices. Either Use Photoshop or lash out on one of Canon's rise and tilters. That's a lot of money for a limited use lens so I'll probably stick to P/S for the moment. It's a bit of a guddle to use as when you've finally managed to stretch the top of the verticals out to parallel you discover the whole building has shrunk in height and now it has to be pulled up again.

I've noticed a big increase in their use by estate agents, (realtors), in recent years, sometimes with very strange effects as the top of the buildings can look wider than the base.

Anyway, thanks guys.

D.

You could try GIMP.  That's free. 

Mike

Good suggestions. Thanks.