Actually, a "qualified" welder would probably not come with his "certificates", since his/her previous employer paid for them. Some are charitable, but at several hundred pounds per test, not many.
A welder coded on pressure vessels/pipes would not be affordable for rubbish skips...
Of course, if you wish to get a welder tested for every technique and position, that would be good news for the testing establishment. Giving them work for a week or two, and a lot of money. And since the testing is usually done at the workplace, occupying that for much time.
Another problem being...they need retesting at intervals.
Most work needs the welders testing to some degree...many contracts specify the degree of competence needed in welding.
Personally, having seen many quicky "welders" put down some of the most beautiful-looking welds, which gave then failed spectacularly on bend tests, I would expect a lot more testing take place.
It was explained to me, by a self-trained welder, that "a weld that looks good, is good".
Which is a load of tosh. A vertical-up weld looks like rubbish to a non-welder, while a vertical down weld, done by MIG, looks beautiful.
The vertical up is the business, the vertical down is car-body-repair stuff, at best.
(I'll not go into basic coated mma vertical down....)
While you're at rubbish skips...take a look at the lifting lugs. An 8 cubic metre skip will have a fair few tonnes hanging from those lugs. Good luck with the legal case if anyone gets hurt by a failure.