Need help finding an obscure and difficult to find seal for my leaking Shower Cubicle
For anyone who encounters a similar situation, I did just find that the channel under the door needed filling with some clear silicone sealant. Once I did that then the leaking stopped. 

I have no idea why the sealant was missing, maybe a previous tenant removed it because it got mouldy and looked bad. 

Either way problem solved and thanks to Jim and brhans for the pointers that got me to the correct solution.  

Hope that helps someone else.