if you buy from the guy on ebay, when you receive the ecu and blackbox you need to fit them to your car (easy). then you will use the red key chip to teach the immob your blue keys. unfortunately you need 2 blue keys for this (2 unique blue keys with different codes, not 2 copies of the same key).
so this means you need to get your blue key copied at timpsons, but tell them to use the code from a different key. you can use the code from any fiat system1 key (mk1 punto, bravo, brava, marea, cinq) so try to borrow a key from a friend with a fiat to use their code. also get timpsons to make another key using the code on the chip from the ebay seller, this will be your red key, mark it appropriately so you know which is the red key.
then you have all 3 keys you need and you can teach the immob your 2 blue keys using the red key. this is a simple 1minute procedure you can do yourself, instructions are available in many previous threads.
the most important question to ask the ebay seller is if the chip he has is from the red key. if it isnt then the parts he is selling are worthless and useless, without the red key chip you cant use them.