Cold atom technologies open windows of insight into a wide range of complex physical phenomena. For example, atom interferometry is a process in which a matter-wave is separated and recombined through interaction with laser pulses (analogous to optical interferometry), with a readout signal depending on the matter-wave phase evolution and sensitive to tiny forces or fluctuations. A differential measurement performed between multiple interferometers over a long baseline will be sensitive to signatures of gravitational waves, ultra-light dark matter and other fundamental physics phenomena. I will discuss the scientific goals and experimental implementation of the Atom Interferometer Observatory and Network (AION) [1], a new consortium between seven UK institutions that will develop a series of increasingly sensitive detectors based on atom interferometry on the strontium clock transition. I will discuss the interaction of ultracold atoms with ultra-light dark matter and gravitational waves, and will describe the development of quantum technologies necessary to support the goals of this new generation of detectors for fundamental physics, focussing on our work at the University of Cambridge on optical methods of manipulating ultracold atom clouds. [1] L. Badurina et al, “AION: an atom interferometer observatory and network”, Journal of Cosmology and Astroparticle Physics 5, 011 (2020).