Mira still support the Sport model shower with spares, and whilst it probably is the heater element which has blown, that's only a guess and you need a proper diagnosis before you consider ordering anything because it could be several things which stop it from heating. So long as the rest of the shower is in reasonable condition, then it's worth getting it fixed, but as I say it needs to be done by a competent person (Plumber with the appropriate Electrical certification) since there's water and electricity there and it's not a DIY job unless you have adequate technical expertise.
Sparks (the Plumber)
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water not heating up?
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