Tonight, I have been mostly following DJCruicky's instructions to remove the glitching that is still present in the latest WIP. And sure enough, it worked! On top of that I also think I've managed to stop the objects appearing in the platforms and the player's feet no longer gets buried in the platforms if you approach it at a certain angle (this also means that the bug that mihcael reported has now vanished). However, it has had the side effect that you can no longer run at full pelt over small gaps which is unfortunate.
Just for Lonewolf10 I've also added a pause key
I guess the only real gameplay element to add now is the powerups so I will start work on that later this week. After that, it's a question of level designing and playtesting and then adding sound effects and music as and when.