Hi there, Ewan. I totally get it, you loved how straightforward Pro 2012 was, and now it feels like the newer versions are all over the place when you need the simple stuff, the time and materials tracking.
However, Sole Trader Plus won't do what you need because it doesn't have time tracking and inventory. QuickBooks Online Plus does both, so that's the one you'd need if you want to track time spent and materials bought and sold.
Whether Plus is worth it or if an accountant is cheaper depends on your volume. For occasional jobs, an accountant will be simpler, but if you track transactions regularly, Plus offers the control that Pro 2012 did.
For any further questions, feel free to leave a comment below.