The concept of autoplay exists on a V6, although there may be some differences with how this operates on 4K/UHD or a 360 - that others with the relevant setup can hopefully chip in with.
"When watching a sky uhd boxsets watching a episode in fantastic uhd the next episode is only in HD. Iv tested this on a few box sets now and it's the same, is there a fix for this? Is this a known issue?" is helpful clarification of your issue.
Out of interest, when the follow-on episode is playing in HD.. is there a UHD version available? This would help rule out the possibility of there not being a UHD version, thus causing fallback to HD.
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