Pipe stat location

hi all, bear with me as I try explain best I can. Stove with a back boiler vented system heating rads & water. Pipe stat currently approx 800mm from the union at the top of back boiler. Water in cylinder is untouchable which obv means pipe stat isnt bringing on pump early enough. Pipe stat definitely inaccurate as it’s set to 25 degrees. Using my IR thermometer I took these reading just before the stat switched the pump. Pipe at stat location 49 degrees. T piece upstairs where the 1” pipe rises from the floor 82 degrees. Union where this pipe enters the cylinder coil 72 degrees. Water in cylinder 74 degrees. Can’t figure out how the pipe was 30+ degrees hotter in hot press compared to top pipe of stove. I know my stat is totally inaccurate and I plan to replace it. Question is am I better off leaving the stat close to boiler or would it run the pump more effectively located in the hot press on the flow pipe. Also what is a decent pipe stat, the current is EPH. Thanks in advance