They had different pack options, but I think all the options were the same price. I got the option 1: 5 X 10g pack and 5 X 5g pack all for 7GBP. They had one option for one 100g pack, so the others were probably combinations between 75g and 100g total weight.
edit:
http://www.craft-products.com/polyform-plastic.asp
http://www.wisdomking.com/product/aquaplast-t-18
seems to be called "moldable craft plastic" or similar
I know firsthand that JB Weld is horribly messy, and smells bad as well.
Maybe they fixed those problems?
Its properties are here : http://sugru.com/about/ : and even to my first glance it seems completely different from JB Weld. Did you bother to look at the web site before asking your question?
This is put so well I don't know what to add to it.