Ali, please forgive me if wrong, but I'm making an assumption that you are not a qualified electrician and are doing this at a DIY level:
Please stop, and consult a Part P registered electrician. There are several reasons for this:
1) This work requires 'signing off' and registering with your local building control office (assuming you're not in Scotland) and is not something you can do yourself
2) Anything you have bought on ebay that does what you are describing is almost certainly used, could be faulty or possibly even counterfeit and doesn't comply with British Standards
3) You are changing the fundamental characteristics of your property and this could be very dangerous
4) You will not be able to proceed further without disconnecting your incoming mains supply and to do so is illegal, to continue without is just blind stupidity!
Do a search here on the forum for a sparks in your area who will help you out.