Maybe contact Dimplex, quote their claim back at them, tell them the lamp has failed and clearly not performed as they claim it would and ask them what they propose to do about it.
How old is the fire? Would it be under warranty?
Trading Standards may take an interest if Dimplex has made a false claim.
Have you looked for Dimplex Spares to see if the lamp unit is available?
Fghhdds
November 2020
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