Hi Donna, The Horn uses fuse #23 20amp, the reverse lights use fuse #13 15amp, but these fuses also power other items.
#23 also powers the indicators
#13 also powers the brake lights and the control of the dipped beam.
#23 is the first fuse on the left very top row
#13 is the 2nd in from the left on the top row of the bottom row of fuses
If you would like a copy of the fusebox layout contact me on nige110162(at)hotmail.co.uk
nigel
August 2010