Gas and electrical wiring next to each other

Hi

My builder is putting a megaflo and system boiler in the external garage and running a gas pipe and electrical cable from my kitchen. Both pipe and cable are basically next to each other in the same trench. The electrical cable will presumably power the megaflo and system boiler. He said something about it's better for the system to have its own electrical circuit.

2 questions

Is it safe to run a gas pipe and electrical wire next to each other?
Also are these pipes waterproof as the trench is currently uncovered and it's about to chuck it down?

A gas pipe will be waterproof, cable should be fine unless the end connections are exposed.
Not a sparks just an old retired gas fitter!
Not sure about current regs on sharing a trench but certainly would like to see some protection over the services before back filling.

From memory I think it’s 25mm electrical cables have to be away from gas pipes, and 150mm from outlets and electric meters