I'm going on 26th too with my 7 year old daughter, from Birmingham to Rila and doing a learn to ski package. I have been before but not for many years, she has done a couple of dry slope lessons, but we're both looking forward to it.
We fly out on the 4.40pm flight is that the one your on Karlos?
Just take private lessons. I payed 15 Euros for 1.5 hours of lessons. I learned more in one hour private lessons than in one week ski school !
You'll never will find cheaper private lessons in Europe !
I was there last week ! super skiing conditions ! super week ! The best holiday ever in my life !