If you don't perform the earth continuity test or are unable to obtain a measured value within the limits specified in the IET CoP but deem the appliance to be safe you need to justify the decision. For example, if a Class I appliance has no accessible conductive parts then an earth continuity test cannot be carried out but you should record this fact. Similarly, if the measured value is above the recommended limit and you consider the appliance to suitable to remain in service then you need to justify why.
Trying to cover all bases....
1. Are you taking into account the resistance of the protective conductor in the power cord when determining the continuity limit? This is sometimes overlooked.
2. Are the accessible metal parts connected to protective earth for safety purposes rather than screening or shielding? This can be difficult to determine as it is usually not obvious. Parts connected to earth for screening or shielding do not have to meet the same requirements as those connected for protective reasons.
It make be a case that you are finding equipment that does not meet the requirements of the IET CoP. This is always a possibility and its best to keep in mind that the purpose of in-service test and inspection is to access the safefy of electrical equipment and not to make it "pass."