I am quite confident it is genuine, it does not smack of a scam at all. The action to take is call a phone number, not click dodgy links.
Googling this phone number (02476 378 330) shows that it is for Tritons UK Customer Service Team and they do indeed even have a Shower Replacement Service – https://www.tritonshowers.co.uk/help-and-support/after-sales/shower-replacement-service.
The email starts with the text:
“We’re contacting you because we believe you may have a Aspirante 8.5 Gloss White electric shower.“
We do in fact have that exact model, they will know about it as I registered the warranty with them 7 years ago.
Going back to the original question, can anyone advise whether £199 fitted is worth it for a 7 year old shower, or should the original item be expected to give plenty more life?
Cheers