| As Old Yella says, B&Q do a wide range of different sized mesh in different colours (plain stainless would be best for yours rather than gold though!) which you can buy in various size sheets.
A radiator sized sheet (about the same size as an A4 piece of paper) is about a fiver - I bought one to make up a mesh for a carbon v-piece.
You only need to make a slight curve in it to follow the line of the radiator. You can then bend the edges around (use a thick pair of gloves to save your fingers) to hold it all in place. Wind pressure will stop it falling off and hold it in place anyway.
As long as you make sure you keep the wheel/mudguard clearance it will be fine.
Don't worry about the odd stonechip though. We all get them and it will take a major dent in the rad to make any difference in efficiency. | 
antonye
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