Terry Wyatt supported a very clear physics case for an e+e- 90-350(500) GeV collider during his talk on the overview of the European Strategy for Particle Physics, at UK HEP Forum 2015. Check his talk here.
The FCC-ee in a few words
The FCC-ee, formerly known as TLEP, is a high-luminosity, high-precision e+e- circular collider envisioned in a new 80-100 km tunnel in the Geneva area. With a centre-of-mass energy from 90 to 400 GeV, the physics program could pave the way towards the discovery of physics beyond the Standard Model, casting light on unanswered questions, such as dark matter, the baryon asymmetry of the Universe, the hierarchy problem, the stability of the Universe or the nonzero neutrino masses.