Just following on from this....the box is still not working,ive noticed that at the back of the box i only have 1 input cable from the dish,do i need 2 for it to work properly,sky dont really want to help as i installed it myself with help from a friend
This is your problem, the Sky + Boxes have twin tuners in them which allows you to watch another sky channel whilst recording another.
To do this you need two input feeds from your satellite dish or you will have to watch what you are recording if you only have one feed.
That explains why when you try and watch a different channel at the same time as recording you can't watch it as the sky box is using the only sky feed to carry out the recording you asked it to do.
You can watch the channel you are recording though if you wish.
If your telly has freeview built in you can use that whilst Sky + is recording if you have an aerial plugged in for freeview.
The only way around it is to see if there is a spare satellite dish input/aerial cable port free on the LNB on the satellite dish and run another cable from there to your sky box.
That way you'll be able to watch and record at the same time.
There is a good chance if the only other sky box in the house is your parents HD box, you ill have a Quad LNB fitted to your dish that have 4 ports on it and one will be spare as there using two of them and your only using one.
I hope this makes sense mate.