Ollie;- ignore the Troll-Creatures that have been trying to put you off. There's no reason why you shouldn't have a play around in your own trees. As long as there is no possibility of harming anyone else around you then there is no problem. You are entirely responsible if anything bad did happen and I'm sure you were aware of this before you decided to try it. Our culture in this country is far too risk averse already, I'm surprised that some on here are echoing that. There is obviously no substitute for experience but as someone else said;- the basic concepts of tree climbing/surgery "are not rocket science" at the end of the day.
Plenty of people even free climb trees without falling out, we are not that different from other primates after all. (I'm not suggesting that anyone does this by the way! I used to as a kid and growing up. No way I would do it now though, it would be extremely dangerous and most times impossible I reckon if you were trying to work and use tools.)
If you were asking for advice in order to profit from your activities then I agree with the Trolls that we as trained, qualified and experienced arborists should NOT be encouraging you. But you're clearly not so there's nothing wrong with us giving advice and opinions. Maybe this is a case of "knowledge is power, hence let's keep it to ourselves and fiercely guard it". I don't think that's very fair. We should all share knowledge, experience and opinions:- that's how we learn and also the whole point of this forum, surely.
Anyway, we digress..........
I agree that some kind of friction saving device is a great idea, and actually almost a must if you're going to be moving around and up and down a lot from one anchor point in the tree. From the point of view of protecting the tree, reducing your fatigue and enjoying yourself. I am pretty sure that reducing friction at the anchor also shares the load more equally between both sides of the rope if using the doubled-rope-technique as well.
I would go one step further than the cambium saver and use a pulley as well, attached via a karabiner. That really increases mobility. Though if you do try that then you need to have complete confidence in your friction hitch as that becomes the only braking action in the whole system.
Have fun, but stay safe!