The field of exoplanet atmospheres has advanced rapidly in the 16 years since the detection of sodium in the atmosphere of HD209458b. Giant planets on short period orbits (`hot Jupiters') have been key to this progression, due to their relatively characterisable atmospheres. Optical transmission spectroscopy revealed the first detection of an exoplanet atmosphere and has continued to play a vital role in atmospheric characterisation. In this thesis I present optical transmission spectroscopy of three hot Jupiters and place these in context within the LRG-BEASTS transmission spectroscopy survey. My ground-based transmission spectrum of WASP-52b revealed the presence of clouds in the planet's atmosphere and evidence for stellar faculae on the host. This study demonstrated that HST precision could be achieved from the ground. I also present ground-based transmission spectroscopy of HAT-P-18b. My precise transmission spectrum was well fitted with a Rayleigh scattering slope at the equilibrium temperature of the planet. The absence of broad sodium and potassium absorption led me to conclude that a high altitude haze was present. Finally I present a transmission spectrum of WASP-80b. I found that a haze was likely present in this planet's atmosphere and my transmission spectrum was inconsistent with a previously claimed detection of pressure-broadened potassium. My results are in agreement with the emerging correlation that cooler planets are less likely to have clear atmospheres. However, this correlation is still tentative. The LRG-BEASTS survey will test this relation and help improve our understanding of the underlying physics driving the formation of clouds and hazes in exoplanet atmospheres.