Thanks for your comments, and thanks again for your help, it's made a big difference
Yes, I actually noticed that bug myself after I posted
I think it's been there a while but it's only since I added sound I've noticed. I'm really not sure what's causing it at the minute, it's very strange. It seems like very occasionally something is appearing where it shouldn't be (i.e. on top of the player). I'll have to take a proper look at that.
As for the levels... yep, they get a tad hard! I think five and six will be toned down a little so there aren't so many 'leaps of faith' as it's largely trial and error at the minute. Mike is doing a sterling job taking the time to design levels so far, he's becoming quite prolific! If anybody else wants to contribute too that'd be good... there's always room for more
My next task is to do the high score table, complete with loading and saving. I've done this successfully in the past so it will hopefully prove reasonably painless (now that sounds familiar...).