It can all be done in the car. There's some sequence to it but it does require the/a master key.
I'm sure someone on here has done it... Fess up.
Alternatively if you're near D1 Customs in Loughborough, Steve can sort you out or Patrick Chambers down south south south
If not too late...done with instructions taken from a post on here (which I saved and printed off to sit in the car with) - for central locking and alarm:
1. Begin with the old key out of the ignition.
2. The DRIVER'S side door should be OPEN and unlocked. CLOSE all other doors including bonnets.
3. Within 5 seconds INSERT the old key into the ignition and PULL it out TWICE.
4. CLOSE then OPEN the DRIVER's side door TWICE.
5. Insert old key INTO the ignition then REMOVE it.
6. CLOSE then OPEN the DRIVER's side door TWICE.
7. Insert the old key INTO the ignition and LEAVE it in the ignition.
8. CLOSE the DRIVER's side door.
9. Switch the ignition to ON then OFF.
10. REMOVE the old key from ignition.
11. The door locks will now cycle to confirm the vehicle has successfully entered programming mode.
12. PUSH and HOLD the LOCK and UNLOCK button for 1.5 seconds on the new key remote being programmed. As soon as you let go PUSH the LOCK button and HOLD it for 2 seconds.
13. The door locks will cycle to confirm successful programming of the new key transponder. If you have any additional transponders to program repeat step 12 if you have no additional transponders proceed to step 14.
14. OPEN the DRIVER'S side door. Programming the transponder is now complete.
For the immobilser:
Now that you have the newly cut key and the master key, you can program the Toyota transponder key. Sit in the driver's side of the Toyota vehicle. Press and release the brake and gas pedal simultaneously.
Insert the master transponder key. Do not turn it. Push and release the gas pedal 5 times within at least 15 seconds of inserting the master key.
Press and release the brake pedal 6 times within 20 seconds of completing step 3, then remove the master transponder key.
Insert the newly cut transponder key into the ignition, but do not turn. Press the gas pedal once.
Wait up to 2 minutes or whenever the security light on the dashboard turns off. Once the light goes off, remove the new transponder key and press the brake pedal once. The new transponder key should now be programmed. Test the key by attempting to start the engine. If the engine does not start, repeat the steps above.