The cheapest are often "PAT checkers" that only offer pass/fail, a good choice for non-skilled staff to do internal testing after a brief course, but no good for anything unusual.
In my last job we had the Seaward Primetest 100 which our technician used to PAT test all of our equipment. It is basically a manual tester, but that was for internal compliance and not as a service and the main time-consuming aspect then was getting the opportunity to take stuff off-line to test it. The PAT database in this case was a manually updated spread sheet, again not that efficient but it doubled up as an asset register as we always had new stuff tested before it was put in to use.
As
@Risteard said if you are doing this as a professional service you need to make it fast and easy for yourself, so automated recording, etc, and matching labels printing would be essential.
As with all things, there are lots of cowboy operators that offer dirt-cheap PAT testing "service" that is not worth even the low price as they don't do a proper job (mostly they don't inspect for damage or check the right fuse is fitted, and often they seem to have monkeys that don't even test properly).
So if selling your time you need to be sure you can compete on quality and have a convincing case that will make folk realise it is worth getting it done correctly. That might go well as an extra to offer clients who are already happy with your work.