Professor Green wrote: but I've got it sitting on 24 °C which is already a fair way above the optimum for this yeast.
Where'd you get that from (24C)?
My observations, I find for WBAB washes the ferment vigor of EC1118 is better/higher at the higher end of the temperature range.
For fruit washes EC1118 is vigorous enough at lower temperatures.
Lalvin EC1118 technical data sheet http://winequip.com.au/wp-content/uploads/2015/01/EC1118.pdf:-
MICROBIAL AND OENOLOGICAL PROPERTIES
• Recommended for White, Rose and Red wine production. Highly recommended for secondary fermentation.
• Saccharomyces cerevisiae var bayanus
• Desirable Fermentation Temperature limits 10-30C.
• Alcohol tolerance 18% v/v *subject to fermentation conditions.
• Low Relative Nitrogen demand (under controlled Laboratory conditions)
• Short lag phase and high fermentation vigour. Cooling may be required to control this high vigour.
• Very Low production of H2 S under low YAN conditions.
• Low production of SO2 binding compounds.
• Moderate Relative potential for SO2 production (can produce high levels of SO2 under low nutrient conditions, up to 50mg/L). Generally considered to be neutral to MLF.
• Killer factor Active.
• Low foam producer.