Reddit reviews The Venomous Reptiles of the Western Hemisphere (Comstock Books in Herpetology)
We found 2 Reddit comments about The Venomous Reptiles of the Western Hemisphere (Comstock Books in Herpetology). Here are the top ones, ranked by their Reddit score.
Here's a study detailing venom expenditure on various sizes or Crotalus sp.: http://www.annemergmed.com/article/S0196-0644(09)01560-1/abstract
Here's a decent book well worth the purchase, it covers this subject quite a lot: http://www.amazon.com/Venomous-Reptiles-Hemisphere-Comstock-Herpetology/dp/0801441412
If you require something a little more comprehensive, I'll have a look back at the lab tomorrow to see if there's something hidden away.
It doesn't exactly cover what you asked for, but to my knowledge there hasn't actually been a study done specifically on this subject. There's just theories that have been derived from other studies that have been done.
Base on your comments, you live in southern portion of the UK. Therefore, I think this book should at least cover you for now. If you plan on heading east, let me know!