It sounds like your accountant may also be providing book keeping services too, so £100 a month pretty fair.
I can't stand QuickBooks. I've got no issues with sticking all my stuff into a spreadsheet each month- I quite like doing my own book keeping so happy to do that as it generally takes an hour on a wet day each month to photograph paper receipts and collate/input everything else from various sources (email, ebay, check the bank statement for finance going out, email compoanies who haven't sent a vat ticket with a materials delivery!)
If you don't service and repair your own work truck you're basically wasting your money.... maybe. Maybe not if you don't have the skills and knowledge to not f it up!
QuickBooks is only as good as the data in. VAT is something you really don't want to get wrong. When you start dealing with things on finance, grant funding, bounce back loans, zero rating on newbuild works and the like, things need to be done correctly. 'I put it in the wrong column on QuickBooks' is not a valid excuse, and HMRC are tedious to deal with to say the least. £50 saved on an accountant is nothing compared to the time out of your business that a HMRC investigation would take, even if you escaped without fines.
If you're taken to time to learn enough about accounting to do your own to the standard of an accountant, then fair play. I do that with vehicle and machinery repairs, and do repairs for other people. But knowing your limits is a valuable business skill. I'm often asked 'wouldn't you make more by working and get someone else to repair your machinery?' The answer is a hard no- but that's because I've tens of thousands invested in tools and skills and can do it easily to above the standard of a professional repair shop. Not so with accounting!
'You're basically wasting money then' is a bit flippant. It sounds top me that Chris knows the value of his time, and knows saving £100 a month is chicken feed in comparison to the hassle it would incur particularly if it went wrong. Think about that customer we've all had, who decides a tree surgeon is too expensive, so heads down to the power tool section at B&Q for a chainsaw 😉