Hi Alan, when you say speedo “not working as it should” do you mean it isn’t working at all? or is working but the needle is jumping around?.
If it simply isn’t working it is likely to be the cable, E Rider should be able to supply one for you and it is fairly simple to fit, if it is jumping around it simply needs the cable greasing.
The horn is located behind the large front plastic panel which is below the headlight.
Batteries are easy to find online, at you nearest golf buggy or mobility scooter dealer, or via E Rider, I assume you have the early version of the Model 30 which has sealed lead-acid batteries? if so they are 12v 20ah batteries of which there are 5 in total, these are widely available, but need to be ‘deep cycle’ batteries specifically designed for electric vehicles and not just standard batteries.
Hope this helps.