sintra is just abs plastic isnt it or something close to it abs would work just as well mate i used craft foam for im asuming the templates much easyer to work with and what part of the Uk you from bro?
I work in a lot of museums, & many of their graphic panels are made from Foamex. I managed to liberate a large sheet from a recent visit (......no.....I didn't wrench it off the wall & leg it!!! it came out of a skip ) It's really nice to work with,easy to cut with a stanley blade, but it can snap if you try to bend it cold, if you heat it with boiling water it softens up nicely.
I've also found it helps if you "V" the back of any sharp bends as well as heating it.
So far I've made about 50% of my chest armour & it weighs 500g. The rest of the stuff I have to make, including backpack, will weigh in at around 1.5kg, & I don't think 2kg is a massive amount of weight.
I'm also gonna use a product called Cellite in order to keep the weight down.
It's a honeycomb constuction sandwiched between 2 very thin sheets of aluminium.......stong as hell & it weighs naff all!!!
You can't bend it, but it works well as straight sections, I'm using it to make my cannon mount & the main structure of my backpack.
We use it quite a bit at work, I know it's hellish expensive, but you should be able to pick up some off cuts from a local scrap dealer. Some boy racers get theirs from scrappies to use to protect the underside of their nice shiney engines.
I've only used 3mm. That seams to be the most used and I had to buy it in a full sheet. When you go smaller you might as well use foamies because it's not structural. Since it's PVC, I've used PVC glue from the plumming department to glue it together, I've also had good luck with ABS glue.
Also, check out Sitra armor on YouTube because they have a lot of techniques for shaping it. StormTroopers usually us ABS.