I've lived in Nundah / Banyo for years and landscaped two gardens. I've always found the guys at Nudgee Road Landscape Supplies very helpful and knowlegable. Their prices are usually a lot less than other suppliers for the same product and they have a great range. Local delivery is very reasonably priced if you need soil or mulch in quantity.
They can usually give you a couple of recommendations if you are looking for a specific trade. Happy to recommend!