I think that the 'working group', if we actually got around to meeting

is the best way forward re quality of restorers/traders.
To compile a guide like this though is very difficult, as customers will ask for just a repair, or a proper restoration, or both.
The only way to ensure that the job has been done correctly is to have a full photographic history of the restoration. We always supply this in CD, email or both forms so that the customer is aware that one, the job has been performed correctly and two that we cover ourselves.
You would be surprised how many customers come in for some work,get an estimate for it ,then when we get into the job , other issues appear that were known to the customer but they failed to mention, or when rebuilding a car you find the electrics do not function correctly,and on questioning the customer admits to it not having worked when it came in.
We used to put everything right into the price, but now we give cars a full test before starting work, just to make sure that apart from the booked in work ,everything else is okay. If not then the estimate will be amended.
John's idea of folk enrolling on courses is fine if you have the time funds and inclination. You will also need the facilities and equipment to perform the jobs required and be 100% certain of your skills.
We have seen many jobs by 'so called' good DIY'rs and have been horrified at what they think is good work, on the other hand we have seen fantastic work performed, that would not be out of place from a pro body shop.
Workmanship is only one aspect of bodywork, the raw materials are another, ie panels. The merits of the different manufacturers have been discussed at length on other threads, but the knowledge of which panels have been used is vital. The British made ones in particular Heritage, use good grade steel, which will last and welds easily, the worst are the far east derived ones which arrive rusty and are poor grade steel, do not weld consistently, and often blow through.
The fit of most panels is average, I dread to think of the shape a minor would take if the panels were welded together as presented rather than taking time to re shape and manipulate them into the correct form.
Lastly preparation, is the key word with and bodywork. Its good policy to strip off all of the original black paint that covers repair panels, (wings are okay) and re paint with a zinc rich weld through primer. This offers good protection to areas like box sections that cannot be cleaned up after welding. Welds should be cleaned up too with a wire wheel or local shot blasting, then zinc primed again. If this basic good practice is not performed then the job will not last and your on the slippery slope of possible of short term repairs.
The rest of the prep and final paint has been covered in other posts so won't ramble on
