lost keys, no red key

Hi everyone i have come accross this site in my search for information regarding a problem with my car, and i was hoping if someone could kindly help me with some information

Basicly i have lost the one and only key i have for my car a rover 618 p reg Auto and theres me thinking i could just take the barrel out and get a ky re-cut ,,errr no !! i have since learnt it has a transponder in the key which means re-cutting the key is not an option.

Here is what i have just found out am i on the right tracks,basicly this is called the PATS system a device in the key has a code which is recieved by a another componant in the barrel and this then tells the ecu that the car can start..

armed with that basic info i have a couple of questions can i swap the ecu from another car with the ignition barrel and key ?

these models come with an without the PATS can i use the ECU and ignition from a none pats car as long as it,s the same model ?

am i abit niave when i think i can just swap ecu,s over lot key aside is there more to it ? or is it just a plug and play operation.

I have been told by rover main dealers that they can fit a new alarm set and programme the keys at a cost of about £300 I would still have to get the car there somehow ?

but i am cunfused though because how are the keys gonna actaully physicly fit in the car do they use a master key then re-cut it ?

i would be very gratefull for ur help and guidiance on the matter j