Complex sentence: In early 2009, Trevor Oakes decided to take a break from the band due to ill health but in the Spring of 2009, he left the band and officially retired from 1 May 2009, meaning his last gig was also at The Cheese & Grain.
Split into simpler sentences: In early 2009, Trevor Oakes decided to take a break from the band due to ill health. He left the band and officially retired on 1 May 2009, meaning his last gig was also at The Cheese & Grain.