Love&Squalor, I did the IC diet for a while, didn't help much, then vaguely did the alkaline diet, helped a bit but up and down, then I got very strict with myself and really stuck to the alkaline diet and I felt better within days, but I did have to follow it very strictly to be symptom free.
When I was doing the strict diet I was eating piles and piles of lettuce, leafy veg, veg & lentil soups, soda bread and snacking on raisins and seeds, drinking just evian, eating very, very tiny amounts of meat, cheese, eggs, chocolate etc. I had to keep telling myself it wasn't forever, take it a day at a time, lol.
I couldn't cheat on the diet without symptoms returning until I began the posture exercises, after a few weeks of those, my bladder function began to return to normal. I've got to say, I'm still not fully recovered - I'm ok and functioning, but still eating alkaline-ish, and still getting the odd bit of burning, but NOTHING like before.
Google 'Katy Bowman pelvis' to find the Katy Says blog which contains the exercises I do.
Re: sex, it was a big problem when the IC was bad, if we could do it it always caused a flare. Nearly gave that up too! I found taking extra D Mannose before and after helped, loads of lube and relaxing before -back massage from dh (if he wasn't too tired) or Paradoxical Relaxation (as described in the book 'A Headache in the Pelvis'). Now the IC is under control, sex can still cause a burning feeling (friction, lol!) the next day, but it's worth it!
Tim Park's book is great - I'd love to try meditation. Incidentally, the classic position for meditation lengthens the spine and hamstrings...
Tim Park also did Paradoxical Relaxation which helps to lower the activity of the nervous system, so reducing spasms and nerve pain.