Replacing gas oven with electric
You need a separate circuit for the oven as it draws a much greater current than the normal ring main.
This site explains the load a cooker draws.

A 240 V domestic cooker has the following connected loads:
top oven 1.5 kW
main oven 2.5 kW
grill 2.0kw
four hotplates 2.0 kW each

This results in a nearly 30A load which will clearly overload the regular 13A ring main.
A hard wired connection is where the connection is permanent and not through a normal plug and socket.