Thank you both for replying AllanR and dop2000
Unfortunately I can't share a project, as it's almost a full game.
The code looks like this ...
However, when the player object stands on the platform_moving_small object, the player doesn't move with the platform. Very odd.
If I change the movement of player X to look like this
The player moves fine (as 47 is the Platform_Moving_Small.Speed instance variable)
But this leaves us with only ever having one speed for platforms. So how can I use the speed instance variable with this Set X ?