Are they all the same?

I have just obtained a Hornby Q1 which has been fitted with all the 'destils' on the front buffer plank. As I have a terminus - fiddle yard layout my locos need to haul in both directions. I have removed the obstructive items but now find that the NEM dove tail pocket I intended to fit will not slot into the Hornby loco fitting. Are they all the same? I don't really want to force fit the thing if that isn't the way it should be done! Any thoughts anyone? The pocket I had intende to use is a dapol one.
Thanks all.

I recently was swapping around couplings and noticed that they were all mostly the same but didn’t quite fit together perfectly as well as the manufacturer pairings. I did just gently pressured everything together until it fit into place, just very slowly and gently while hoping nothing would break. Sorry, that’s not very helpful. Thankfully nothing no broke on me!