How can i get my cargo 813 H reg started?

Whilst driving my lorry back home after buying it I had stopped 3 times and it started fine but only after it made a couple of clicking sounds. On the 3rd stop when I went back and tried to start it I got nothing at all. All electrics ie lights fan radio all work fine and battery definitely full. But nothing at all when turning on ignition. I had to get a push and she started on a bump start straight away very easily so not anything wrong with engine. Any ideas what to do greatly appreciated thanks Lee