I've just completed my longest solo ride to date! Did around 30 miles round trip from Paisley to just past Port Glasgow. Cycle path almost all the way, and was almost flat for the first 10 miles, followed by some rolling hills after Kilmalcolm where you can build up some speed. Same hills mildly challenging on the way home, obviously, though nothing that would kill the average CC cyclist! Saying that, I stopped twice on the way back
FYI, Paisley is a 10 minute train journey, or a 25 minute ride, from Glasgow Central.
The route can be extended further into Greenock and around the coast. If no one organises a 'proper' route in the west, then this is something that's easy to organise, on quiet paths, achievable by (almost) all, and an be extended or shortened depending on weather, and fitness of the group.
Check out maps here
http://app.strava.com/athletes/317427. I split today's ride into 4 shorter segments.