Good news! I found my keys. They were inside the tissue box on the table.. god knows how they how got there.
I had a chat with the mg/rover dealer and they explained what they could of done. Firstly, provided I show some ID, they are able to ring up somewhere to get a code, which allows them to get a key cut. This cost £15 for the key and £15 for the phone call.
Once I have the key I'm able to open the car and disarm the immobiliser using the code inputted into the door. He explained it as a series of left and right turns equal to the number in the code e.g. 3 left, 2 right, 6 left, etc. Once entered I have 30 seconds to start the car.
Next is the key fob. They wanted £75 for the mg 3 button version! And that wasn't including programming, which I think they quoted at around £60. So all in all, very glad I found them and didn't have to fork out these ridiculous prices.