I'm moving house this week, there is already a satellite dish there and I have bought a second hand receiver. Is the connection process between receiver, dish and TV relatively straight forward? I'm a bit puzzled as the receiver has one input socket from the dish, but the cable coming through the wall from the dish has two cables to connect. Is this standard?

The two cables thing is most likely because the previous owner had Sky+ (which uses two tuners to enable two channels to be simultaneously received/recorded/viewed - hence two cables needed). If your box is a standard Sky one, you will just need the one cable - either will do. Connect it to the only socket it'll fit and you will be away. Give Sky a call before you move in and explain the situation, don't let them convince you that you need to pay £60 installation for their man to come round and plug it in. Also, depending on what subscription you go for (if any), contacting them early gives them time to send you out the viewing card. Oh, and the box needs to be connected to the phone line for Box Office and other premium services to work. It's in their T&C's that it is connected to the phone line, but if you prefer not to/the cable doesn't reach, they rarely do anything about it.

I thought the condition of having the box connected to a phoneline only applied if you wanted a free box and a cheap/free installation?

Just to clear up the obvious ......

Is one coming from the dish and one from an analogue arial?
Does the dish have 2 LNB's for recieving from more than one satellite?
Do they both work? One may have been disconnected.
Is one actually an extension going out to another room?

It is actually just one cable coming through the wall, but it splits in two a couple of inches before the end of the cable, and there are then two identical plugs to go into the Sky box, when there is only one socket for it to go into. The aerial cable is completely separate. I think the Sky + explanation sounds the more plausible. I am only going to be using it for freesat, and I have paid £20 for a viewing card, so I am going to do the rest myself. I will let you know later this week when I have moved whether it has worked or not!

Sounds like Sky+ wired with shotgun cable, (figure of 8). Should be a simple case of just plugging one of them into your receiver.