Moving from BT Complete Wi-Fi with 4 disks

[rm113]

Hi,

I have a large, long house and my router is at one end. 
I am considering moving from BT to EE after I got an email suggesting it.

However, I see that I will only ever get 3 disks and the Smart WiFi Plus router. 

Is it possible to procure and extra disk?

[Wandering10101]

delay/avoid if u can. My new Smart WiFi Plus 3 extenders to the SH+ if MUCH inferior to old BT router and discs. I cannot revert since they demanded return of old kit.  New white rectangular extenders seem to have less range and seem unable to chain down a long large house with thick walls.  I am considering cabling the whole house!! I had a home visit. everything worked until about 12hrs after his departure...