Can I use a dipole antenna in the loft horrizontally?
Guessing you can like coaxial antennas....or not....?
Will work, not sure how well but the only problem may be a tricky swr issue. Everything depends really on how spacious your loft is. Try to keep it in as much free space as possible would be what I would probably do. Also don't forget about the directional properties you will have best in 2 directions. The ends of each 1/2 of the dipole will be affected most in a negative way.