Hi,
If you have Sky+ already in the home, you could use one cable for the Sky+ box and one for the TV.
You would lose the ability to record one channel while watching another on the digibox although you could set the Sky+ box to record one channel and watch the other on Freesat if it's available (i.e. no movies or Sky sports etc.)
As rewerb has mentioned, you could run another cable from the LNB on the dish to the TV. The ability to do this will depend on the type of LNB you currently have.
Don't think you will be able to split the signal from one cable to two tuners.
Cheers,
Cofnchtr.