Hi Dave, 
I have spoken to a colleague to get accurate information and understand that your main luggage will be stored by our overseas agent before you go on the boat from Puerto Maldonaldo to the Amazon. On your return, you will be reunited with your luggage before flying from Puerto Maldonaldo back to Lima and then on to your return journey to the UK. 
In terms of packing I have taken this from the information that is being mailed to customers on their upcoming departure... 
Recommended Clothing/Essentials 
A Smaller bag is recommended to take with you during your stay at the Amazon 
Hand sanitiser 
Camera 
Torch 
Strong insect repellent 
Personal Medication 
Sun block 
Sun hat 
Sun glasses 
Walking shoes/ boots 
Comfortable shoes for the evenings 
Thick Socks 
Shorts/ three quarter length 
Trousers/jeans 
T-shirts long and short sleeved. 
Waterproof jacket 
Fleece 
Light jacket with a hood 
I hope all of this helps.  
Kindest regards, 
Julia