I have had PCOS for many years and like you, was prescribed Dianette, it made me so depressed, I felt suicidal. I went to see someone privately, after reading online how PCOS was treated in the States using a diabetic drug called Metformin, at the time, it wasn't licensed for the treatment of PCOS here.
I've been taking Metformin for years now and fortunately have had no side effects, I was last taking 500mg daily and that seemed to regulate my periods, but I was also very fit at the time, which helped. Then after meeting my partner, I gained over two stones, so my periods stopped and I'm now taking 1500mg daily to re regulate things.
I'm trying to get my weight back down now, as I know it helps the condition not to be overweight. You should probably be under a specialist at the hospital 3bis, GPs' don't tend to know the ins and outs of conditions. It used to be Gynaecologist who dealt with the condition, but now PCOS is deemed as a hormonal problem, so perhaps ask to be referred to an Endocrinologist.