Which box have you got? A BT Vision box or a Youview box?
As Stuart asked, do you have Infinity? If so and you can't see the sports channels at 507-512 and the extra channels at 413 onwards in the guide then check the following
Go to Youview>Settings>System Information>Software versions and check the ISP Configuration.
It should be 29, if it is 28 the box is not configured for multicast channels and needs a software update which has to be initiated from the BT end.
If you don't then sport / extra channels are not available to you on the Youview box