As you've mentioned too much heat, yet you live in the UK, I can only assume you're talking about Yucca elephantipes, the houseplant? Does sound like too much heat - these really need an unheated room in winter, and are better for being stood outside during summer. Needs minimum temps of 45 degrees, but does like to be cool and not hot, needs as much light as possible, water liberally spring through autumn, sparingly in winter. Needs a deep pot with very good drainage, repot every 2 years.

Many thanks for that Bamboo. Great help.