The BBC Olympics channels will occupy EPG numbers 550-573 for HD and 574-597 for SD. Also Eurosport 3D will return to its former channel number 523, apparently for the French Tennis Open.
Sad to say that VM hasn't added any other new HD channels since last autumn and the only one confirmed as "coming soon" is Alibi HD which is supposed to launch in July. BBC HD becoming BBC2 HD doesn't count, so when can we expect some new HD channels Virgin Media? It's been a very long wait and the arrival of the Olympics channels at least confirms there's no technical capacity restrictions denying us more HD content.