Having been refered to in this post, a very important tool for easy cutting of the bare polystyrene boards was custom built because of saving some money.
While these can be found on the market, good models with adjustable heat may cost over 30 euros. By analysing the kind of hardware I would need, I found that it wouldn't be such a big problem because I already had most of the stuff in my electronics scrap containers.
The only thing I didn't had laying around was the support for the hot wire, which I had to buy. I just used a metal support with a wooden holder for a conventional saw, which proved to serve the purpose just fine: