With GOLD and FreeSports recently being replaced with their HD versions on Virgin Media I thought I'd scroll through the EPG looking for obvious candidates to follow suit.
Regional differences and not being in the same package are the main reasons channels might not be replaced any time soon as far as I can see. Here are the ones I think could be done easily.
The following list is based on what I can see on my EPG, and I'm on Mix pack so if something isn't available on a lower package and I've not realised please say so.
BBC4 - has no regional variations
CBeebies - as above
CBBC - as above
Paramount Network - the SD channel has higher number so no number adjustment required
4Seven - HD on all packs (AFAIK) and HD version is on Freeview HD
Quest HD - same as 4Seven
BBC News Channel - has no regional variations
The following can be switched in Scotland
BBC1 Scotland - it's one of the few BBC1 regions to have regional HD variant
BBC2 - from 2019 when BBC Scotland Channel launches BBC2 will become the National version which I believe is what BBC2 HD on VM is
STV - the recent press release about their new deal said STV HD was replacing SD version on VM
The following channels I'm only suggesting as I believe I read a year or so ago they no longer do regional advertising variations anymore.
Channel 4
Channel 5
Like I said I may have made errors, so please poke holes in this.