You do know that you will only get what is available for free don't you, no matter where you point it? I don't have sky but I thought it was scrambled and had to be paid for to unscramble.
The main UK channels are on Astra 28.2E, but as mentioned, you'll only get the free-to-air channels without some sort of additional viewing cards and/or subscriptions.
Unless your dish is motorised, it will only be able to point to one satellite anyway.