A quick pedantic note in response to a query.
David Jacques describing Blick Mead "The springhead and springline water temperature is a steady 10-13 ºc all year. The experiments that confirmed this observation were conducted by Pete Kinge of QinetiQ using fixed thermal imaging cameras and by Tim Roberts."
This steady consistent temperature provides the useful property of unfrozen water for drinking by the wildlife as well by humans and also encourages early grass growth for grazing. Blick Mead would have been one of the larger such spring fed pools in the area. The consistent temperature in a grove of trees would also provide for the panting hart cool water and shade in the summer.
But these are not "warm" springs as usually understood. Warm springs or thermal springs are those where hot water from great depths in the Earth rises to the surface. Blick Mead's springwater is at the normal temperature of groundwater, with maybe a slight increase in temperature over neighbouring springs as the water is coming from under a greater depth of chalk than at them as the land rises steeply directly behind Blick Mead. (Groundwater temperature varies with depth - the ground temperature shows seasonal fluctuations to depths of about 15 m where the temperature is approximately equal to the mean annual air temperature(8 - 11° C in the UK). Below this the ground temperature increases at, on average, 2.6 °C per 100 m due to heat flowing from the interior of the Earth. Mean temperatures at 100 m depth in the UK vary between about 7 - 15°C.)
TEMPERATURE GRAPH AMESBURY
Webb, B. W. and Zhang, Y. (1999), Water temperatures and heat budgets in Dorset chalk water courses. Hydrol. Process., 13: 309–321. doi:10.1002/(SICI)1099-1085(19990228)13:3<309::aid-hyp740>3.0.CO;2-7309::aid-hyp740> provides a good understanding of similar waters and references for further research.