Haha thanks! I've been working on this for quite a while now. In fact you can see versions from development stage under the name 'dodge' (that's what it was called back then).
I've implemented your solution, and I'm glad to say that it works, so thank you!
The only thing which could be better is the fact that the player renders before the new co-ordinates for the mouse mapping is set up, so when you try to move the player outside, it looks a bit like the HUD elements when resizing the browser, is this supposed to happen?
Also, the game is set so that any finger (mouse) movements are amplified x2 (I'm going to make this sensitivity adjustable in the future). The offset doesn't have to be there, you can just release the finger (or click button) and move it around and it won't affect the player. You can then touch (click) back wherever it suits