AER make light engines.
http://www.mulsannescorner.com/aerturbolmp1v8.html Might have something to do with how difficult it has been to make their engines reliable. Still, they are installing them in Champ Cars now and that must be very exciting with a claimed 1,000 hp.
The 2014 RE article on Rebellion claimed +/- 115 kg and the TS030 unit is apparently close to 100 kg now. It probably varies depending on whether builders include the exhaust, inlet tract or fluids. BMW claimed they could have gone down to 68 kg with their F1 V8 if they hadn't had to comply with the rulebook's limitations.