Freesat can work off your Sky dish. What you need is one extra cable direct from the dish to the Freesat socket on your TV. There's no other way to connect that will work without messing up what you already have. It's the extra cables or forget it.
The above assumes you have some spare connectors off the satellite dish. If you have Sky Plus or Sky HD installed and only have two wires from the dish then you will definitely have two extra connectors available for use. If you have an older Sky installation with just a single wire from the dish then you'll need to go look if there's any extra sockets. Some installs had an LNB (the thing that the wires connect to on the dish) with two sockets, some older Sky Digital instals had LNBs with only one socket. LNBs with extra sockets are available online and in stores. Google for more info.
The above is the cheapest way to get your freesat working. Yes, it's possible to buy splitters and fancy gadgets that will let one dish wire feed two displays but...
___A) they limit your channel choice because Satellite isn't the same as TV aerials so you can't just split a signal - It won't work the same,
___B) these splitters are designed for blocks of flats with communal satellite systems so they are more expensive than getting some extra wire put in.
Satellite cable and the appropriate connectors are available on-line, in shops (aerial suppliers,
Screwfix, Maplin, B&Q, etc) and via your local aerial installers. If you haven't got the gear to drill walls and get up ladders, or you are just worried that you'll mess up when fiddling with the satellite dish then getting an aerial installer to do the job would be the safest bet.
Freesats channel coverage is very similar to Freeview. There are a few channel differences. Go online and check out the TV listings to see where the channel differences are and if they are important to you.
