So, the solution I found for this was actually much easier than I expected.
Once you have selected all the events or region that you want to shift the size of to the left, you do the following:
You NEED to have the ‘nudge’ palette visible along the top, and then just click ‘trim start left’ as many times as needed until the longest one is extended all the way. This button will shift the start of the audio event left by whatever grid setting you have e.g. 1 second.
Dave