Blown concrete lintel

[sheddy]

The concrete lintel above my daughter window has blown out, due, probably to water ingress that has rusted the steel reinforcing bar causing it to rust and expand.
How can I repair this and get it looking like new again (or as near as possible)?
I have seen patch repair stuff at Wickes and wondered if this would be strong enough.

 

[Newboy]

If the rebar has rusted to the extent that the concrete has blown I'd suggest replacing it completely.