Nothing wrong in bringing it in house.
I would suggest the C&G course, there used to be 2.
1 for doing it and 1 for managing it.
I did both, even though a qualified spark.
I have also taught them.
Just give your tester the authority as well as the responsibility to do this.
i.e. if the heater in the MD's office is dangerous, he has the authority to remove it, no matter what the MD says.
Also, get the IET CoP, and keep good records, benchmark everything when it comes in.
I have the Seaward Supernova, this can "run" 230 & 110 V devices to do leakage tests.
If you have a reasonable volume of kit and you are going to take this seriously it is worth going down the software route with barcode labels or tags which the tester can read.
Also, making up "special" test adaptors is very timesaving if the work is repetitive.
Put procurement procedures in place such that your PAT person is advised when new electrical kit turns up and give them the authority to go and check it before it goes into use.
I have just looked at the screws and fixings supplier I think you are referring to.
You are looking at the top of the range one made by a company in Dover I think.
Mine is made by the company that makes the most expensive one on there.
They all have their advantages and disadvantages.
You should look at annual calibration, but that can be done locally in Newport, they have a local collect & deliver service, tends to be a week about, or by mail order, there are a few I can recommend, by the OEM via carrier, or if you have a local electrical wholesaler that your company buys maintenance bits from, they will likely have an annual calibration day where you can drop the instrument off and pick it up within a few days.
The calibration co in Newport are also a sales organisation who represent almost all the manufacturers including those I am suggesting. I know them too and can get a rep to you if you like, they are national.
Crazy really that we are skating around the brand names!
I can possibly get a couple of instrument reps to come and chat to you from the OEM's if you want, honestly, even though you are only looking at one instrument, I know most of them personally, certainly those from Dover, and many from the company in Peterlee Co Durham too.
Give ma a shout if you want to chat about it, I'm in the office most days these days.