Avocado leaves drying?
The leaf tips have begun to ‘crinkle’. Is it due to lack of or too much water, or something else?
Depends where the plant is. As always the problem is over/under watering, cold draughts/over heating!!!
Before you water it again check the compost first. If it sticks to your fingers do not water it as it is wet enough.
Have you moved the plant into a different place? Many plants indoors do not like being moved. Is it near a radiator?
We have a chestnut plant that was in our garden room (unheated). We noticed back in early Dec that the top leaves were going yellow...too cold for the plant. Moved it into where we grow orchids and it is happier so this one liked the move.
More likely to be the dry atmosphere in a CH house. Avocado's are basically trees even tho not suited to the UK climate. Even if it drops it's leaves over winter, you can bring it back to life in Spring. Cool and as much light as possible for now is best if you can manage that.