Renault Megane won't start....relay buzzing?

I have a 99 Renault Megane cabriolet. I have just recently had some work done to it. Cambelt, Cylinder Head, Two valves and water pump replacement. The car was working fine but then cut out. Now it won't start and there is a buzzing/ticking noise coming from a brown relay under the bonnet. Replaced the relay, still no luck. The car seems to be earthed. No fuses blown so any ideas why it won't work?

Cheers