Notice the pattern
Does the temperature change when another tap opens, when the shower mixer is adjusted, or throughout the whole shower? Describe the sequence rather than guessing which component is responsible.
Compare outlets
Tell the service team whether the basin and kitchen have the same issue. A problem at one outlet can require a different investigation from a change across the property.
Mention recent changes
A replaced shower head, plumbing work or a supply interruption may be relevant context. These details help explain the situation but do not confirm a diagnosis.
Keep comfort safe
Check temperature carefully before use and take particular care around children. Stop using water that is unexpectedly too hot and seek model-specific guidance.