logic bouncing loads of silence at end of

Another alternative solution is to move the end of song marker (circled below) - just click & drag it to the end of your song. (You might have to scroll for a while to find it)! This can sometimes move if you do a really long take, or drag unused regions & paste them after your song end.

I always check where this marker is when bouncing, as it seems to ignore cycle loop selections. Personally, I prefer to have "include audio tails" checked in the bounce preferences (to retain reverb & delay tails at the end of a song)...

This happens, when you enabled "include audio tail" while bouncing AND one of your plugins creates some noise, mostly analog-emulations. Look for switches named with "analog, 50/60hz, analog noise etc.

Alternative to yoyoBen's answer (which will also solve your issue) is to set a cycle (loop) region for the length of your entire song. When you bounce it will start bouncing at the cycle start point and stop at the end of the cycle point no matter what.