Well, Dedicated Micros actually.
Fan sounds like a chainsaw on the CCTV DVR.
DM offer a 'fan kit' at =A378.
Seller on Ebay offers a fan with DM plug for =A316.50
Shiny Hardware offers a fan for =A33.97, cut the plug off and attach the plug from the old fan, solder and heatshrink up.
DVR no longer sounds like a chainsaw.
That's a cuppa tea earned.
Owain