Important advice on isolating your generator
REMEMBER: Your generator MUST be isolated from the mains supply for safety and efficiency. Otherwise, power can back-feed along the lines and you could electrocute the poor chap down the line trying to fix the mains supply, or even give a nasty shock to your neighbours.
So, make sure a manual transfer switch is installed by a qualified electrician. This is fitted between the meter and the consumer unit, connecting the building, and you plug your lead from the generator into an inlet connector.
Finally, a low impedance earth spike will also need to be installed.
This is a viable and useful way of providing backup power and gives you the flexibility to use the generator for other purposes, since it is not permanent.
HOWEVER. As a general note, DO NOT attempt any of this without, at the very least, a long talk with a qualified electrician. It will be worth it, and is essential for safety.