Right then, the recordings that I made this morning were:
Frasier
Channel 13 - Channel 4+1
Start Time Fri Dec 18 09:59:25 2015 GMT (Scheduled: Fri Dec 18 10:00:00 2015 GMT) {Started 35 Sec early}
End Time Fri Dec 18 10:29:59 2015 GMT (Scheduled: Fri Dec 18 10:30:00 2015 GMT) {Ended just about spot on}{
Duration 30 minute(s). (Scheduled: 30)
Frasier
Channel 13 - Channel 4+1
Start Time Fri Dec 18 10:30:00 2015 GMT (Scheduled: Fri Dec 18 10:30:00 2015 GMT){Started spot on}
End Time Fri Dec 18 11:00:23 2015 GMT (Scheduled: Fri Dec 18 11:00:00 2015 GMT){Ended 23 Sec late}
Duration 30 minute(s). (Scheduled: 30)
Homes Under the Hammer (to use both tuners across the changeover time of Frasier.
Channel 1 - BBC ONE HD
Start Time Fri Dec 18 10:00:02 2015 GMT (Scheduled: Fri Dec 18 10:00:00 2015 GMT){Started 2 Sec late}
End Time Fri Dec 18 11:00:14 2015 GMT (Scheduled: Fri Dec 18 11:00:00 2015 GMT){Ended 14 Sec late}
Duration 60 minute(s). (Scheduled: 60)
Both Frasiers recorded just fine and dandy with ads at the start and end of both. There were no arbookmarks in the recordings, but as I was using AR, I suppose that's normal. So much for that experiment then.
Shame I deleted the original ones that gave me the problem. Next time I have a prob, I'll not make so free with the delete so that a post mortem can be held.