She did have thrush about 1 month ago, and she also lost about 1/2kg, but seem to have put most of that back on, I just put that down to learning to walk.
She was also ill in January and lost about 800grams due to dehydration, but once we got her rehydrated again in hospital she put that back on within a week or two.

She has been drinking this much water for quite a while, so before all of the above, she isn't really lethargic, quite a busy little girl, and she has one day sleep most days some days not, of about 1.5-2.5hrs.

It might be worth getting her checked just in case, she had extremely low BLS of 0.9 when she was born, but that was due to her prematurity and was sorted out quite quickly and we haven't tested them since.

You haven't made it worse at all, I guess I am just trying to guage how much water would be "normal"/"average" as such, and the need to drink overnight even in the cold weather has got me wondering if other bubs do the same.