1. Department of Physics, University of Warwick, Coventry CV4 7AL, UK
2. BAA Variable Star Section, West Challow Observatory, Wantage OX12 9TX, UK
3. Isaac Newton Group of Telescopes, Apartado de Correos 321, E-38700 Santa Cruz de La Palma, Spain
4. School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ, UK
5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
6. Centre for Extragalactic Astronomy, Department of Physics, Durham University, Durham DH1 3LE, UK
7. Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA
8. CBA Belgium Observatory & CBA Extremadura Observatory, Walhostraat 1a, B-3401 Landen, Belgium