25mm square mesh may give some reassurance you are protected from larger stones etc, but I suspect a direct hit from something heavy enough to cause a refrigerant leak may still be able to burst through, more often than not. I suppose every little bit helps. . I'd be more convinced if someone testify ,,or produce photographic evidence of a significant stone 'strike' that was prevented. Anything it has been able to stop would probably have left marks or distortion on the mesh.
It looks to me that most of the blockages and fin flattening is due to insect strikes and airborne vegetation, much of which would still get through a 25mm mesh. Anything fine enough to protect from these could seriously impede airflow through the radiator.
I would be very cautious of trying to clear the fins with a power washer , or even a hose, or airline. These can easily flatten the very delicate fins, and in some cases might have been what actually caused some of the flattening in the first place.
Maybe a blowing them out, ideally from behind, using a photographers dust blower (a squeezy rubber bulb) might work, with a bit of delicate manual clearance and fin straightening. But it would be extremely tedious.
You can buy bug removal spray. I dont know if this might speed up the decay of insect remains. Perhaps some of this and gentle washing will help.
I looked at the Wickes site .Their site analysts have spotted a recent surge in interest in the product.
