The runners are quite sticky anyway, but by the sound of it, they have been replaced slightly out of line. If you look at my 'How to' remove the seats post, you'll see that mine were retained by six bolts - three each side. Morgan being Morgan, yours may be a bit different, and you may or may not have wooden spacers under the runners. When my seats were out I applied some spray grease to the runners, and this did help. I suggest that you slacken off the bolts on one runner, and see if there's any jiggle room. If not, loosen both and jiggle. No need to remove completely unless you want to do a thorough lubrication job - probably not necessary.
