There are a number of locations where you can enrol on the modular certificate in arb (level 4). Tree Life are expensive but have a good reputation. Warwickshire College is well worth looking at, the level 4 is just a few hours on a tuesday evening, which means you can continue to work. Might also be worth going on the basic tree inspection course too (run by the AA). I would thoroughly encourage you to go for it, we need more expeirenced arbs like you moving up through the ranks.
There seems to be a lot of academically well qualified tree officers out there who have never actually worked with trees, and that is a worrying state of affairs. How can anyone realistically carry out professional tree inspections, recommend sound and practical tree work specifications, prepare work contracts and deal with contractors if you've never spent any meaningful time working with trees?
