In addition to the previous answer, in the UK, in order to comply with Building Regs that sort of job MUST be done or supervised by a Competent Person - which frankly you are not. (Legally or practically.)
The advice that you have been given about getting an electrician is good. Do it quickly before someone is killed or you have a fire. BTW if the latter, your insurance will almost certainly not be valid.
V
October 2008
Providing I understand what you say correctly - I would be very worried. If you remove the main Neutral wire you still have working lights !?!
This means that the return path is via Earth somewhere in the property. In the interests of safety this should be resolved immediately.
No wonder the RCD tripped when you installed the new consumer unit - it compares the current in the Line and Neutral and wants them to be within 30mA of one another If current is running to earth then the RCD will always trip - as it should.
Quite why you wired the consumer unit to a plug and tried it in various sockets I'm not sure. Presumably there was no output load on it and no current being drawn - so the RCD will never trip.
Get a Sparky in soon.
Peccavi
October 2008
Automatic Answer
We may have found other answers which could help you.
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix switches and sockets.