I have worked for Hawkesworth.
You will attend a short days in house training and issued with the necessary equipment, tester, leads, company shirts, logging equipment etc. Be aware you will need to sign a contract that basically says you cannot work in the industry for a few years when you leave them. You will also be asked to get your City and Guilds within 3 months although I was able to wait a year before they pressured me for this. You will also need to take out public liability insurance and insurance to cover their equipment which you are renting from them.
You make up your testing technique as you go, I noticed when I started that almost all of their engineers did not know you have to use the probe to test a Class 2 appliance. Working with various engineers you will slowly work out all the shortcuts that allow you to do up to 400 tests per day, some will do the job properly and you will see others just putting stickers on, this will be annoying when you are working on the same job and the other guy is earning double what you are. This is where you self regulation comes in.
You will get paid extras for repairs, fuses and plug changes etc, again you will see some engineers just ticking boxs to say they have changed a fuse, so that is one way to increase your rate. It takes about 6 months or so to gain the knowledge to earn £100 a day, you will have good days and bad days depending on the environment your testing in, i.e in a dirty factory you might only achieve £50 a day compared to a clean organised office, guess you have to take the good with the bad.
My work was fairly regular to begin with, the few months around xmas seem to be very quiet. Payment by cheque was always quite reliable, as was delivery of stock, plugs fuses etc which you must purchase directly from there, no a bad thing as its the lowest price you will find.
I found that Hawkesworth did give preference to engineers who do the most tests per day and are willing to travel the furthest. This was the bad point for me as I realised I was getting little work because the engineers just putting stickers on were doing up to 400 tests per day and so getting more preference of work, penalising me for trying to do the job by the book.
Hope this helps.