The power lights shows that power is getting to, and through, the on/off part.
No signs of life or lights then suggests a failure of the main control board.
Be aware, there may be an underlying cause for the board failing and you would need to have suitable test equipment to check the electrical components and wiring in the appliance.
Simply replacing the board may mean the new board fails in the same way.
The boards are expensive (over £100) so I would suggest getting someone in to repair the appliance.
Then, if the new board blows, it's their problem and not yours.
You can get a fixed price repair from some companies, British Gas currently offer a one off repair for £125, inclusive of parts and labour.
No charge if they can't repair it.
Click here for more details of their offer
Hope this helps