"it is very common for trees to be literally topped in half, a practise which is becoming increasingly frowned upon within the Arb industry."
Steve, re pruning....this sounds as if the practice of topping is open to interpretation, I would be more assertive, What about something like;
"As our company follows British Standards 3998 for treework, we will not carry out 'topping' of trees."
"When reducing the size of a tree's crown or removing branches we endevour to maintain the natural shape of the tree."
Something like that, no half measures, when someone asks me to top their tree in half, I just say,
"Sorry but my standards don't allow for me to do this, I'm a Certified Arborist and someone could come out and look at my work at any time and if they see a poor pruning job I will lose my accreditation, I also have my reputation to protect"
Then I tell them what I can do. And if they don't like it I walk away.
With your website you gotta set out your stall right from the start so that people know exactly where your coming from.