Hi Rocky.
Yep. Got the mesh from local hardware superstore (B&Q)
I measured the apertures of each rad then made template from card.
I then finessed the shape on the card to get a snug fit and made the pattern in more durable cardboard. Laid it on top of mesh then added 8mm or so to each edge. I then folded the mesh around the template( 90 degree to front edge) and trimmed the return edges to the desired depth. Popped the lower one in to test fit and again finessed where needed.
Look at the lower rad pic and you'll see st/steel lockwire going from one side to t'other. It holds the mesh in position.
Top grill is a lot easier. just measure the width (36.5cm sounds correct) depth 15cm and add 10mm all round. Fold the 10 mm back on itself. this gives a little clearance gap between mesh and rad. Its a very snug fit so no need to secure with anything. Can't drop out because of the plastic rad shroud.
Look closely at the pic and you'll see what I mean.