Filling the gap between wall and tiles. What product?

[Collision]

Thanks for all the suggestions guys. I've been hanging back until I could get some pictures up but I'm still unsure of using sand and cement to fill the gap.
Is there going to be enough give in it to allow for movement?
Also it's going to have to be a lime mortar (well that's what the wall's pointed with) can I use SBR with that?
And will that(lime mortar) make a difference to the flexibility to allow for movement?

 

[AliGage]

Lime mortar is pretty flexible as is.

 

[White Room]

If you use lime mortar personally I would'nt add any sbr to it.