Just out of curiosity, I switched over to this yesterday, but then found that whenever I changed channel it upset the recorder so much that it re-booted each time and always came back to Vintage TV again.

In the end, the only way I could get out of this loop was to perform a complete re-tune. The videos on Vintage TV are very poor quality, but in the ad breaks it looks almost like HD. Is this an internet channel and if so, aren't these normally only available via a subscription service?

Vintage TV is indeed an Internet channel (IPTV). Some are subscription, some are free. I can get them on my Sony TV, but they often hang the TV or it reboots. They're mainly of interest to foreigners or Christians. If you don't want them it might be worth deleting the channels (mostly 225-248 plus one in the 'Adult' section) so you don't select them by mistake.

There's a bug that means the box reboots when you try and change from Vintage TV. I believe it's been reported to Humax, so they should be aware.

You can get out of the loop by quickly changing channel when the box reboots, before Vintage has loaded.