I had private lessons for 2 years running, (right from scratch) with a guy called Stefan who lives/works out of the Titanic Bar (opposite Rila). He was great, if your really serious about ski-ing and want to do it well he's your man & he didn't cost the earth.
I had a private lesson whilst in Boro this year with a local instructor called Jordan. 1hr lesson for my Mrs and I was really good. Did about 3 or 4 turns and he gave us pointers straight away which really helped out.