Not checked recently (3+ years ago) but if you want to a have fully functional setup then you will need a complete keyset, key unit and possibly a new ECU as well. This is going to cost your £500 to over £1000.
HOWEVER - you could look into/research ECU immobiliser removal. They are some companies that can do this BUT unless you fit an alternative Thatcham rated immobiliser then you car will be uninsured. You may be happy with this but it is an ABOSULTE MUST that you declare and check with your insurance company that only your theft part of you policy is invalidated. Some companies my invalidate you whole policy and cover which could leave you totally uninsured and as financial risk for the rest of your life.
There are also aftermarket fuel injection system options but they tend to be motorsport/performance based products, generally don't have built in immobilisers and are generally expensive.
