I just had a brainwave and downloaded ShiftN, which was recomended on a photography forum. I've no idea if this is the best Lens Correction Software or anything but I'd like to thank Oblique Human for bringing my need for this to my attention! It only really becomes so evident as to be problematic in 28mm architectural shots, but boy does it show once it's been pointed out. This would have been particularly embarassing had I shown the couple of very sharp shots I've been lucky enough to get in large format
Thanks, man. I'll keep on plugging away.