how to wire 2 new lights on a new twin switch?

Adam is correct in both respects,picking up a supply from an existing switch is possible but does not conform now to good practice.Also your terminology ie twin as opposed to 2gang switch poses questions where is this switch being sited in relation to the existing switch?,how do you propose to run your switched supplies to you lights?. The word competent comes to mind nobody is going to sign your death warrant.Have a sparky to set you straight.

Guytawe
May 2010

Your "only possible power suply" is the remote end of a 2 way switch, with no neutral.
I suggest getting someone in (an electrician) who can sniff out a useable power supply.

Adam
May 2010