latching relay problem

It may be easier to put the light on a delay timer.  Say, a 10 minute delay.  Then, once you press the button the light will come on and then stay on for 10 mintues.  If you need it on longer you could just push the button again.

If the module you are using doesn't have latching ability and that is definately what you want, you may need to look in to finding a similiar module with programmable outputs.  Otherwise, you will need some circuity between the output of the module and the relay that controls the light - like a D flip flop set up to toggle. 

you can use this setup to accomplish what you need

The 12vdc output would drive your relay that controls the light.  So, in addition to the relays above, you would need a relay(s) with a 12vdc coil and contacts rated to at least 240vac and 5A.

In all the years I have been on this forum I have never seen anyone post that they got this relay configuration to work, so if you use it and it works be sure to post back.