Hi, I used a Bushbaby Cocoon and absolutely loved it.  I used it all the time for the first 7 months, my daughter loved it too even more so when she could face outwards.  The "between leg" section wasn't too wide and she has no problems with her hips now (at 14months).  It has fantastic head support and is made to be parent friendly in that it's easy to put on/take off and spreads the weight really well so that you don't get back ache.  When I first purchased it I took it to a chiropractic appointment so my practitioner could see how it worked, she was pleased as the weight tends to be held around the waist/hips therefore not straining the spine.

If you go on the bushbaby website they do deals sometimes.  John Lewis sell the product so if you want to try it out they should be able to help you.  Also I have noticed a lot of people selling theirs on ebay once they've finished using them, which I'll be doing once baby number 2 has outgrown it.

 We loved it so much we've just bought the Bushbaby Premier back carrier and hope our daughter enjoys that as much as the Cocoon.

 Whatever your choice, good luck.  I do appreciate your predicament, I was the same but read lots of reviews to help my decision.  A good website to use is Mumsnet.com.