TV M is Virgin's no-frills "Freeview" equivalent service, & is basically provided free with a landline. The VHD box is a single tuner, non-record box. Virgin sometimes offer V+HD recording boxes as second boxes to ex Sky viewers, but these are refurbished units & can cause more trouble than they are worth. Only TiVO boxes can stream programmes to eachother, & even this facility is restricted due to rights issues with some broadcasters. On demand programmes are also dependant on your subscription level, which for TV M will be very basic.
If you want HD content the only TV package to go for is XL, which is basically everything excluding the premium channels like SkyMovies.