What you'll earn PAYE is a broad spectrum depending on the firm and what they value you at, but I've found that guys entering the industry as climbers nowadays are offered about £11 - £12 ph if they are green.
£13+ if they have a few years experience or pick it up quick, show efficiency, interest and prove they are reliable, with a good work ethic etc. After that, team leader roles seem to average at about £14 -16 ph. London it's often more.
The trouble is, you have to somehow prove that you're worth the firm giving you climbing jobs. Especially if there are several trainees eager to get any climbing they can. It is a lot safer, easier and quicker for the firm just to use the experienced climber whenever they can. I've seen guys go and get all their tickets, turn up first day bright eyed and bushy tailed, only to get slowly ground down by the prospect of only doing small trees for the next three years. In my opinion, PAYE jobs can be harder to progress in.
Your climbing background will help you. But Arb can throw some major challenges your way. Add a chainsaw, -4°C, sideways rain that leaves you frozen to your core, 100ft in the air, wind that makes you question the structural integrity of the tree and a lot of weight and you can quickly find yourself in a whole lot of trouble. That aspect of the job definitely isn't for everyone. There will be times where you experience near misses and you'll begin to understand the risks involved.
If I were you, in today's climate, I'd give myself three years.
Year 1, I'd seek an employed gig. Get them to fund some tickets and work until you've gone past the payback clause that'll be in your contract.
Year 2, I'd approach some domestic arb contractors to get some Subbing work as a groundie. As many firms as you need to get full time work. 3 days a week with them, 2 days a week with him etc etc. Learn the ropes as it were... tell them that you're keen to try climbing. Keep them sweet by turning up when you say you will, keep your attitude straight and get after your goals. But keep yourself booked up as much as you can. Firms that like having you on board will begin to offer whole blocks of time. Like 3 months of work 2 days a week etc. Then you can start to plan around that. (Arb can go quiet all of a sudden so be careful there...)
Year 3, you'll know if you like it or not by then. If so, push harder for climbing, learn what you can online, from books and through watching the more experienced guys. Start to think about how you can excel at the career. It's not all about knowing "what" you are doing up a tree, it's about knowing "why" You are doing it.
Or some blokes come into the industry and decided they are happy chipping, cutting, working on the ground. There are too few like that because the money only starts to get better if you climb, or start out your own company.