The current version of the COP has been in force since about 2006, and it still has 16th edition terminology in it. However, the current version of the Electricity at Work regulations have been in force since 1989, and the Health and safety at work act since 1974.
There is a load of other legislation, which is also listed in the COP, and it all falls under the remit of EAWR and HASAWA, all three clearly state what needs inspecting and testing, and why.
In a nutshell, ALL electrical equipment requires some sort of maintenance etc, i wont quote rules and regs, but the first few pages of the COP explain it all very clearly, even down to who has responsibility etc etc.
The COP costs about £35 not £200.
Cheers..........Howard