Samsung Warranty Repairs
A "Whatever Works" to this service - my Note 4 suffered a sudden failure recently (stuck in a boot loop, and then booting to recovery mode only). As I still had time to run on its contract, I took it into the service centre in Manchester.

Once they'd confirmed it was under warranty (by scanning the code in the back of the device) they carried out a mainboard replacement. The only downside was the time it took (roughly a week, from initial inspection, through awaiting the part to handover back to me). A good service though, with good communication from them at all stages.
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