OK, I have finally found the environment report comparing the impact of using cloth (looked at cotton terry nappies) and spossies (disposable nappies)..
To be honest it is too complicated for a simple minded person like me to understand, but there are a few things I have noticed in the comparison.

1. It is based on the production of just cotton nappies (non-organic) so includes pesticides and other nasties that can be used in the production of cotton.
   We know that many nappies are now made from bamboo and hemp, which are greener alternatives.
   Organic cotton is also widely available.
   
2. Nappy users were asked how they washed their nappies, and here's what their survey showed (page 63):
   • Percentage wash 90° C - nappy 32.
     1 %
   • Percentage wash 80° C - nappy 0.
     0 %
   • Percentage wash 70° C - nappy 7.
     1 %
   • Percentage wash 60° C - nappy 35.
     7 %
   • Percentage wash 50° C - nappy 7.
     1 %
   • Percentage wash 40° C - nappy 17.
     9 %
   Nobody washed cooler than this.
   I'm not sure who they asked, but I have never washed my nappies hotter than 60, and I only wash that hot when very dirty.
   The wash care instructions on my nappies says 40 degrees.
   
3. Apparently the average nappy user has 47.
   5 nappies (page 53).
   I think I have far too many at around 35.
   
4. Also 80% of nappy users soak their nappies (the water used in this and the sanitisers both have an environmental impact.
   )(page 55) I would say that dry pailing is more popular.
   5.
   49% of clothies use conditioner (someone should tell them they shouldn't be!)(page 55) 6.
   9.
   5% of us find the time to iron our nappies (page 56).
   
5. "We have assumed that tumble driers are used to dry 19 per cent of nappy wash loads.
   This is considered a weak assumption, and expected to be a minimum.
   " From page 64.
   This might be true.
   It's worth looking at how much energy this uses up.
   I personally use the tumble for around 15 minutes to soften nappies.
   
6. Page 65 "We have assumed that nappies are kept for reuse and that wraps/pants are disposed of with domestic waste.
   " I wouldn't throw my wraps away.
   What does kept for reuse mean? Around the house as rags (all 47.
   5 of them) or passed on to be used as nappies again.
   (I took it to mean use in the house, as it specifically talks about selling on prefolds used in nappy laundering services.
   )

Conculsions Here's a bit from the conclusion (page 122) The results of the study suggest that the focus for improving the environmental performance of disposable nappies should be on the disposable nappy manufacturers and their suppliers whereas, with reusable nappies, it is the user who can achieve the most environmental gain through energy efficiency drives in the home:

• disposable nappy manufacturers should focus on weight reduction and improvements in materials manufacturing; and
• reusable users should focus on reducing energy consumed in washing and drying.
  

I agree with this.
It just shows that how we wash our nappies really does make a difference to the environment.
(and with the price of electricity, our pockets too) Here's a link to the article (all 209 pages of it!) [http://www.
environment-agency.
gov.
uk/commondata/acrobat/nappies_1072099.
pdf]