Take the word of people who haven't done what they are giving advice for with a grain of salt, ex: if the parent's haven't RTW'd then they might not be the best advice-givers.
I'm going to give it to you straight:
Since you've already booked the trip, here's my recommendation: SAVE SAVE SAVE - or take a loan out / have credit card.
36 pounds per/day is pretty low for 2 people traveling with the destinations you've chosen. All those countries except for Thailand and Fiji have a high standard of living and thus are more expensive.
If you can, try to double your money to 72 pounds per day, or cut your trip short by a couple months - you'll be glad you did.
I sincerely hope you have fun. And while I may be a relatively cheap traveler myself - with activities and myself alone, I'd be struggling to have fun with that budget.
FYI: it cost me $16,000 to travel for one year (living cheaply, yet having fun).....in 1992.