Rennie has been in association management for most of his working life, starting with the Australian Meat Industry Council in 1998. He has been at CEO level of industry associations for 21 years and is currently the CEO of the Federation of European Self Storage Associations which has more than tripled in turnover over the past five years. He is also the CEO of the Self Storage Association UK, building it to be the second largest association in this sector in the world. Rennie has worked with a range of associations on three continents, often assisting them in developing their strategic direction. He has also been a board member of several charitable organizations, mostly in the early childhood education sector. He has an MBA from Deakin University and is a member of the Oxford University High Performance Leadership Programme.