I'm currently having 2 problems with my tablet related to casting . Firstly If I cast from Chrome Browser it's often slow to connect and sometimes doesn't work at all ie just have the Chromecast background displayed on the TV . Secondly if I'm watching a Netflix program the ff , Pause , Stop buttons drop off the bottom of the tablet screen and won't reappear and if they do happen to appear they are greyed out and inoperable .Is this a known issue ?

Reboot sounds a good step
http://allaboutchromecast.com/chrome...ata-reset-fdr/

That was the first thing I tried , it doesn't seem to make any difference .

How far away is the device from the router?
What interference is there that might cause the signal to drop out ? eg neighbour's signals, other devices adjacent to the device
Are all apps up to date?

The router is in a seperate room across the hall , there's also a Wifi extender (Sky) not sure if it's needed .

tbh, I would ask for this to be moved to the pc & hardware forum for a wider response.
I think you need to eliminate router/wifi isseus first.