Just to throw in a different opinion. What i found from driving mine with a fixed seat, as it was angled and not too far back it catered for everyone from me (6'2") downwards without needing adjustment. Actually i can't remember anyone being too short to reach the pedals....
That said i'm not knocking anyone who does fit a sliding seat, especially if they're "well ard", as while i can see that sliding seats can be useful, I'm not totally convinced that they're needed in a Sammio/Ribble?
Just food for thought