Setting up as self employed and registering for VAT took about 30 minutes and I did it myself. I think the VAT repayment was about £5k and accountant fees circa £350pa so well worth the effort. I also made quite a bit by being flat rated for VAT and invoicing Brookfield for VAT in my RYR days. You can do your own accounts and VAT in a spreadsheet and get your accountant to review before submission.
Just get a proactive accountant who is willing to look at all the best options to save you money, not the easiest for him! I went around 4 or 5 to see how they were before using one.
I few with lots of idiots including one guy who just paid 40% tax like he was employed and didn't bother offsetting any expenses and another who paid zero tax and hoped he would get away with it. Just don't take financial advice from pilots - I may have mentioned this already