I've got the TV XL Package, it's basically all the channels (except SkySports and Movies) - in other words, about 250 channels, of which 245 of them are pretty cack.
If you have 37 HD channels then you've got the XL package - just flick 187 on the remote, if it brings up BBC 2 HD, then you've got the XL package, if it doesn't bring it up, then you don't have and you'll have to get it added to the existing package. A threat to leave, citing that you prefer to watch HD stuff usually get's them to upgrade you (this is what I did in May, and have got a free upgrade from "L" to "XL" for the next 12 months