Yesterday the final part took place. Money & goods changed hands in exchange of a non-disclosure agreement. It took several months of effort though, and was seriously harrassed by their solicitors (they probably thought I was some stupid kid they could trick)
Here's what I've learned from this saga:
1. When turbos are faulty, you know it very soon (I already knew that from previous experience, but I was still fooling myself!)
2. The likelihood of a turbo unit being faulty nowadays is quite high actually, even for some NEW ones (through correspendance with experts in the field). I thought even if it's 5%, then the chances of three units being faulty in a row are 5% * 5% * 5%, ie miniscule.
Doesn't work that way!
3. ALWAYS go by recommendation for such services. Looking back, I should have stuck to this rule more rigorously. If anything, I would have gotten a blank stare - lack of feedback in such cases might indicate something dodgy.
4. Do NOT go for the lowest price quote. I knew that already, but human nature being what it is - I sinned (again). AM I ever gonna learn?
Hope this helps others
PS please do *not* ask me to name names, because I'm legally bound to be silent on this one. Instead, find several enthusiasts' forums and ask for feedback regarding any company you plan to use. That's what the forums are there for!