How to get others to understand that my first name consists of two words? I live in the UK and I have a foreign name of the form

Abcd Efghjk

where both words and the space are part of my first name. Due to common UK standard everyone usually assumes either that Efghjkl is my surname or, more often, that Efghjkl is my middle name and proceeds to omit it.

I am fine when people omit it in speech, as Abcd is an acceptable shortening of my name, but I really detest it when I receive emails starting with


  Dear Abcd,


instead of the appropriate 


  Dear Abcd Efghjkl,


I usually let it slide whenever I know this is a one off interaction and point it out at some point otherwise.

Lately I have been at times adding a remark at the end of my emails:


  Just to let you know, my first name is Abcd Efghjkl, with the space. I know, it's crazy!


I would like suggestions on how to deal with this very common occurrence. I see two options, but feel free to add more.


Keep such a message on a need-to basis, in which case I am looking for suggestions to make it more pleasant. Especially, I am not trying to make the other party feel guilty for the misspelling. I am not mad, this is a minor mistake and it's comprehensible given the running convention in the UK. Ideally, if there was a graphical/non-confrontational way to silently point this out, I would resort to that.
Add a fixed message in my signature either with the same tone of the above or a little more formal. I am a little concerned that this might look odd and somewhat aggressive though.


Any suggestions?

PS: I write here as most of my daily contacts where this interaction happens are academics. 

Edit: I am referring to my first name in the above, I do have a family name or surname as well, which in our notation and taking some suggestions from the answers, would be: MNOPQR.
I would make a point of signing my emails Abcd Efghjkl. If they don't catch on after recieving your reply, add a friendly PS just as you have been doing. It's your name and you are completely justified in wanting it said properly.