yeah if he has 5 feeds already he must have an octo LNB so 3 free 2 for your freesat then 1 left spare saves having another dish

Octo's used to be fairly rare and expensive, but are now fairly common.

They did not used to be available with a mini-dish mount, but do appear to be now.

Once you hit 8, to go above this you need to use a QUATTRO (not quad) LNB and a 'multiswitch', effectively you then have unlimited independant outputs depending on the amount of outputs on the multiswitch, although multiswitches can also be stacked.

Some lower end multiswitches can actually use a quad LNB rather than an expensive quattro, but the budget multiswitches do not have great stats.

No, QUATTRO and multiswitches are more for flats etc, and can also incorporate terrestrial on the distribution.  We have used them in several larger houses and houses with annexes/holiday flats etc.

You need to go for a larger dish (80cm) plus with multiswitch installs as a multiswitch will inherently drop some of the signal, as will the no doubt longer cable runs associated with larger installs.  You cannot boost a satellite signal, you need to start off with a nice strong signal before allowing it to 'degrade' down to a useable one.