Just general observations inspired by the tale without any knowledge of what work is in contention, so not meant to be viewed as criticism.
The MOT is an absolute rock bottom standard only applicable to the state of the vehicle on the day, it does not take into consideration what the vehicle could be like in a week’s time. The MOT preparation should be rectification work following a preventive maintenance inspection; it should not be a reaction to what has already failed. In an ideal world no work other than perhaps a chassis wash should be required. Using the tolerances allowed on a steering ball joint as an example, some of the tolerances applicable to components are simply frightening. Given also that sealed for life ball joints can deteriorate at an alarming rate once a small amount of extra free play is present, but which would be insufficient to deserve even an advisory, then differences in opinion over what work is necessary are easy to understand.
Using the example of any vehicle in poor condition being prepared for test in a reactive mode, then if for example £2000 had been spent I can easily forsee how the conversation would go if at the next PMI a quote was presented indicating that a further £2000 was required to rectify defects.
An in-house repair will practically always be cheaper than using the services of an outside agent, paticularly so if the expenditure is viewed in relation to the vehicle’s planned use and age and department budgets.
As mentioned headlight alignment is an old favourite, a failure on this can be prevented easily by booking a headlight check to be carried out at the time of test. This ensures that the alignment is checked on the day on the actual instrument being used for the MOT test. Even allowing for the relaxation of standard, the DVSA preferred instrument is considerably more fenickity than the more generally used devices. Without knowing the actual vehicle’ plated axle weights it is difficult to comment upon the issue of ply rating failure, however the tester at MOT does have attached to his clipboard the plating certificate for the vehicle which indicates the requirement for the vehicle, it would be unusual to say the least for a garage fitter to have the same available.