Thank you for the reply. The flaps on the side of the cooler are permanent fittings. What the parts diagram doesn't show are the brackets to connect the flaps to the armature.
One of the missing parts is shown in the attached EBay advert on the left side of the cooler. The other is indistinct but from the position of the cooler fittings and the location on the armature they are handed left and right and are complex.
The Diiy solution with Dexion may be the only way as £80 for two more rusty bits is not on the cards at the moment. It will need to be positioned carefully though as it critically covers the bottom of the radiator and I don't want to upset the cooling.
Jim