Not sure what categories are now, but there used to be 15 parts to Corgi. 1-5 is the basic that you need, can cost £700 upwards for this part plus time off and other parts are done after this. This means you can test gas installations and not much more. Then different installations require different parts, e.g. boilers, central heating installation, warm air heaters, gas fires, cookers, all should be listed on his card, this is why gas installers have to charge more now. You got a good deal there Rog hang on to his number.
Paul