I use specialists for many of the jobs that require specific kit and expertise. While I have several trade accounts with larger suppliers I generally like to go to the specialist plant growers for specific purchases.
They specialise in mature trees and shrubs https://www.paramountplants.co.uk
I have no hesitation in recommending Tree Frog Services. They are very professional, easily contactable on text, email and phone and have really invested in the kit needed to get the job done. They also obviously have great contacts for the more esoteric stuff. https://treefrogservices.com
I have had the great pleasure to purchase mature olive trees from this company that is meticulous in making sure that the trees they sell are tested and certified. Their biosecurity measures are beyond reproach and the trees are stunning. https://villaggioverde.co.uk