Need to upgrade to a Full Tower with at least one 5.25inch bay (for Optical drive). Budget is around £300 max please.
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Here. Nice ATX tower case with single optical drive bay. It's quiet and discrete but it doesn't have a side panel window (you didn't specify if you want one). It has, however, PSU shroud for hiding excess cables and two preinstalled silent 120mm fans. Hope it would suffice.