When using review sites (such as TrustPilot and Feefo, both of which are well-respected) it's always best to be cautious, as some firms submit fake reviews for their businesses (all of which, of course, are always full of praise for those firms).
However what such dodgy traders can't do is to hide any
negative reviews they might attract. Therefore, when using TrustPilot and Feefo, it's always best to see how many poor reviews there are. In the case of Fischer Future Heat that seems to be remarkably few (and, unless the company employs some very skilled writers, the large number of positive reviews seem to be genuine too).
So the signs appear to be very good:
https://uk.trustpilot.com/review/www.fischerfutureheat.com
https://www.feefo.com/en-GB/reviews/fischer-future-heat-uk-ltd?displayFeedbackType=BOTH&timeFrame=ALL