Key fobs

[Niall]

Explain why it didn't work on my old 306 the previous owner had told me it required batteries and recoding to car

The previous owner lied to you then :p
Circa 1999 PH3 was released with RF keys. They are not interchangeable with the old IR ones. Have a look at both where the key blade goes into the casing. If one of them is a IR one, it will have a small clear LED looking sender. If neither of them have anything like that, they are both PH3