It's not part of a special offer, it is listed as part of M+ and has been for years, suddenly it is no longer available. There has been no change advertised and it still shows as part of M+ on all channel guides on their site and package lists.
I know that doesn't help you, but perhaps Virgin are taking the channel away in certain areas first.
VM don't add/remove channels in this way. If a channel has an EPG number it should be available if you are on the correct channel pack. Either the OP's problem is signal or box related, so this is likely going to be a tech callout job.
Forum team members take several days to respond to posts here, as this forum is designed for customers to help eachother by sharing information. If you want a quicker response, the phone is the best option (150 free from any VM landline/mobile)
Cable customer since 1993. Services: FH TV, Sky Sports & Movies (2xV6), Talk Anytime Phone, VIVID 350, Virgin PAYG Mobile