The problem is that you can't have 2 channels on the network with the same ID.
History HD. on 245 was a temporary channel. History HD (without the dot) on 299 became the permanent one.
The metadata for History HD. in common with Virgins standard policy continued to be transmitted in the background for a further three months after the channel closed, then it is removed, hence your recordings will no longer play.
Its another reminder (if you needed one) that recording of content on Virgin is licenced for timeshifting purposes only, & are not intended for archiving.