I have now put my rivet counting hat on.
I have some good news tinged with a minor possible black mark.
I have the book "BR Main Line Diesels In 4mm Scale" by R S Carter in front of me right now and I have been comparing the 4mm scale technical drawings of body side, front and roof of a Class 37 diesel loco with the example shown in the picture and the shape and wheel and bogie positioning look spot on chaps so a thumbs up there!
However when looking at the image of the roof fan cowling there is not any evidence of visible fixing rivets to this ring.
Then I have the book "Modellers Guide to Modern BR Motive Power" by Peter Kazmierczak as a reference and certainly for the examples of Class 37/4 chosen the model appears to have the correct front pattern headcode and side grills following conversion for c.1985. including the 2 rivets above the headcode which again is spot on chaps!
Loking at the second image of the cab and upper body at an angle there is photograph P37:04
on page 26 of the first aforementioned book taken at precisely the same angle and the shape of the cab and roof profile are a precise match so again spot on chaps!
There may be a question mark over the depth of the headcode rim and light rim under and this will probably form the main area of rivet counting discussion chaps as there is a possible link between this and the extent of the curve on the front of the nose.
The line of the headcode where it meets the nose is not straight at any point and this is prototypical. Any flat spots and it would not be accurate.