Rollacosta,
I'm not going to disagree with your post by no means, but I think arborists here in states have a different view on tree planting, than what you guys have in England.
I've been on both sides of the fence on this one. I come from a nursery, landscape background. I just happen to stumble into arboriculture by accident. There are some firms that do install trees, but as a general rule most arborist don't. This is usually landscapers work.
The reasons are many and varied.
Most new planting occur in new developments for housing. Things haven't changed one bit from the last forty years. All topsoil is stripped from the site. What is left is nothing more than hard compacted clay [ builders loam ] with maybe an inch or two of topsoil sprinkled on it, which has always been handled wet. Not exactly what I would call a good conditions for planting a tree, of course every one wants a warranty, and the guy who plants it is in some way forever responsible for it. Digging holes in conditions like this with just hand tools is really labor entensive, you need a jack hammer instead of a spade or shovel.
Another reason is labor and insurance are higher for arborists than they are for landscapers. Unless you can prove your company is doing say 50% tree planting and 50% tree trimming, you won't get a break on liability and work comp insurance.
Most people just handle the tree planting on their own, they can handle this part, but can't get rid of a big tree or prune one.
I'm sure others have different views on this, but for me tree planting has never really been what I would call a good experience.
It can be a profitable side line, if you can juggle the two businesses, it is hard to do though at least from my point of view, seems you do one or the other, but fail when you try to do both.
Larry