Can anyone tell me the size of the flanged screw in the top hole of the drop link ? 

Hello Terence,

In the absence of other replies to date, the thread diameter - in mm., should be easily determined using a micrometer, or even guesswork - they usually work out in increments of 2 mm. What is more difficult to determine is the thread pitch, of which there are many variants for the same thread diameter. e.g. 1.5, 2.0 etc. 

Any reason you can’t simply wander into your local motor factors and look at the replacement part? 

Not sure if any of this helps.

Kind regards,

Gareth.