I am often asked about chocolate and my recommendations. I am pretty hard core with my chocolate and love 100% Montazuma Absolute Black. They now do a 100% with orange - wow! I buy these from Sainsbury's and they cost £2.50 per large bar, which lasts me about a week.
I also love Chocolat Madagascar 100% dark Chocolate but this is more expensive at around £5.95 a bar.