This may add to the expense unless you can borrow one but using a screwdriver with a torque setting ensures you get all the terminal screws correctly tightened. As I was adding the last circuits to my garage CU I checked the ones I had done a couple of weeks before and they were still spot on. If you have to buy one Toolsatan do a Draper for £65 which is probably the cheapest around.

Whilst on the subject, I was tempted by the BG CU with the mini RCBOs until I read a review by an electrician that as he was torquing up the terminal screws the casing on the RCBOs were distorting and tending to split before he achieved the recommended torque even though his driver was recently calibrated.

Richard