I searched the web and took some advice off fellow boarders (about getting the reflective finish) and finally found a place that was very reasonable. To get two done (they come in pairs) cost just under £80, which I think is okay!
I put the word out on the forum and quick as a flash Michael Carroll came back with the following design.
We decided that the Thrill Suckers would be a bit strange for motorists to figure out so ditched that idea. I then asked Michael if he could put some 2000ad characters heads across the bottom, for ident purposes. He came back with the next design, which is the one we finally went for.
Once everyone said they liked it I sent the jpg off to be made into the actual banners. It took less than 10 days for the finished items to arrive. I unwrapped them and tested them on the car and radiators and they worked a treat.
I tried to upload the finished pic but it's not letting me at the moment, so I will add the finished picture at a later date.