65-66F is perfect for most yeasts suitable for this style, for example, WY1318 (London III).
But active fermentation generates heat, more so the warmer and more active it is. So you must keep an eye on the temps not rising past 66-67F. Use a water filled tote or cooler or so as cooling jacket/heat sink, to draw off the extra heat. Adding 1-4 frozen water bottles a day (or twice a day) to the "water jacket" may keep temps just right.
I often ferment beer like that in my lower level bathroom, during the cooler seasons, as temps are then 65-66F there.
When fermentation slows down you can probably leave it at ambient 65-66F, or ramp up slowly with an aquarium heater in the water jacket to encourage her to finish out quicker. Or wrap a temp controlled heating pad around the fermenter, taken out of the water jacket of course.
Booziness (and off flavors) can have very much to do with higher ferm temps. Best, cleanest results are to ferment at the lower end of a yeast's range, not at the higher end.