Inspection and testing of in-service electrical equipment (referred to as PAT testing) needs varying skill depending on what it is, the boiler is still in-service electrical equipment, so often service contracts are taken out on the more complex bits, in real terms it's a watch my back exercise as often the firm contracted only attend when the item has stopped working.
There is no legal requirement for stickers saying items have been inspected and tested, all the HSE needs is for a safe working environment, and to be frank class II items i.e. no earth connected, have very little that can be tested, a visible inspection is really all that is required.
So it may be what you need is some training for the caretakers, as with all health and safety you need some thing in writing, nearly every place I have worked has tool box talks, the idea is some one who has been trained passes on the information to other workers, so a sheet saying what has been talked about, and a list of signatures so for example you can show the HSE how the caretakers have been shown how to test sockets are safe using a plug in socket tester, and know what to do if it shows as not being safe.
When in university they had people employed to do inspection and testing of in-service electrical equipment, one of the items was a PLC which is an electrical item we were being taught to use, it does not matter what it did, and they fitted a sticker saying it had passed, as part of our training we had to list any possible dangers, and the PLC had a flip up lid to get to live terminals, reading the instructions from manufacturer it stated this item should be fitted inside a lockable cabinet, so technically using them as we were doing as a stand alone unit did not comply for ordinary persons, however we were not ordinary persons, so there was nothing to stop us using them, however when we had a visit from schools then there was a problem, and it caused a problem when we pointed this out.
So when doing inspection and testing of in-service electrical equipment, the environment, including status of people changes if we can pass of fail a piece of equipment, so a radio with a fig of 8 lead (referred to as lead set) would pass in an office, but fail in a car wash, because there is too much water in a car wash. This is common sense, but you need to show the caretakers have common sense.
It is some times unbelievable what lack of common sense some people have, like using a phone on charge while sitting in the bath, it does not matter if mobile phone PAT tester and charger PAT tested, they are not designed for use in the bath, so it is the caretakers that need training, like any other worker. So trained how to recognise class I equipment and having class I tested is a good policy, but simply having some one test everything is not enough.
I had to attend a tool box talk from a safety officer, he stated we should not use anything until PAT tested, and there is never an excuse for breaking this rule, if you look around this office he says, you will see a label on every electrical item. Me being a cantankerous so and so I said no there not, very quick inspection and only around half the items have test labels. Answer was show me, which I did, every lead set because it can be unplugged and moved from computer to computer should have its own label, but they didn't, so it was clearly not a real problem, they had all been tested with the computer or printed they were plugged into, however he had said if we find something without a label stop using it immediately, so following his own rules, he should have closed down the offices until all lead sets have been tested and labels affixed. He clearly could not do that.
So you need some common sense, if the kettle in the property fails, you can't really say sorry no pop noddles until some one can test new kettle.
The big problem with people using their own equipment is the equipment register, we should be able to show the HSE a list of all electrical equipment in use, clearly items which are moved around that is hard to keep track, and we had a code PO in front of the equipment number to signify private owned.