Tony, I've just started fly fishing too and had the same problems as well. I was lucky enough to get some instruction from a professional instructor and he corrected those problems as follows.
1. Whipping sound on forward cast - You are forward casting too soon after your back cast and not giving the lines time enough to come behind you. The trick I was taught was your cast is a slow "TICK-TOCK".
2. Can't keep the line off the floor - This was because I was letting the rod go behind me too far. On the back cast, stop the rod at 12 o'clock and on the forward cast stop it at 10 o'clock.
3. Cast not straight - If you can get the first two things rectified, the straight casting thing should sort itself out.
However, I would highly recommend getting some professional tuition on this as it's much easier being shown something than it is being told it.
Let us know how you get on.
