Hi, a bit late but...
Check this out: one 3-way Littleswitch and one Lttleswitch slave. Set-up would be as follows: three LNB cables to the three inputs on the Littleswitch as close to the LNBs as possible. One output cable from Littleswitch to digital receiver. Littleswitch slave inserted between end of this downlead cable and input to dig. receiver. Slave fly lead goes to pin 8 on receiver-to-TV SCART. Triggering AV on your dig. receiver remote gives voltage to pin 8 on SCART thence to slave which triggers Little switch over the coax downlead. So, no need for Diseq at all. I used this for years on a Panasonic TUDSB20 digibox with the channels I wanted from 19.2 and hotbird programmed into 'Other Channels'.
You can get the hardware here:
http://www.sfmuk.com/ and I see that he has a new switching mechanism for digiboxes.
I used this to switch between hotbird, 19.2 and 28.2 for a digibox receiver in which case one has to use the TV-SKY buttons to fire the slave, i.e. press TV then SKY and audible click will be heard from the slave.