A little late to be contributing here, but I've looked out my glider logbook and can say that I began training for a glider pilot's certificate at the age of 24, with no flying experience other than two air experience flights, both in gliders.
After a total of 42 flights (including the two air experience flights and two sorties in an SLMG for low-level launch failure training), I was sent solo. I had a total of 11 hours, 8 minutes, and had taken just over 6 months. This included two six week lay-offs, due to bad weather, lack of funds and general idleness.
I took the Bronze C (short for Certificate) handling test just four months later, having flown a total of 22 hours, 26 minutes. This included a total of 23 solo flights plus further dual training (75 flights in total).
All of my glider flying training (save the SLMG flights) were 2000' aerotows, and flown in the south of England.
More recently, I flew at a club in the English midlands where the club owner was also a gliding instructor with a nearby gliding club. He reckoned to be able to get me back solo in a glider in about ten launches. Whether that was simply because I was already qualified to Bronze C standard, or because he thought he was able to convert any pilot into a glider pilot in that short a time is another question, and one for others to answer.
Best wishes for your glider training.
P