I lost the original key but the spare doesn't open the boot. know a way to break in?

Not without damaging the lock cylinder for the trunk. Is the spare just poorly cut, or is it the wrong key altogether? I would call a locksmith who can open the trunk for you, usually around $75 for a service like this.

If you are locked out of the vehicle completely, you are best to use a coat hanger over the top of the driver side glass and down to the door lock lever. Be warned that this may scratch your paint. Alternatively, for pre 80 model toyotas, both the key and barrels ware to a point where any similar age toyota key can unlock the door. In some cases the ignition also. Ofcourse the most logical approach is a lock smith.

there is a handle, down by the gas-cap opener, that will open the trunk. If trunk is what you mean by boot. Or as we used to call it in Texas, the Turtle.