Fair comment.
I've never had much success with the local Berks Birds recording site, but a reasonable suggestion. This suggests historically you get sightings of Tree Pipits maybe April to occasionally August here (Berkshire), while Meadow Pipits are much more reported, including in the last few days.
Comparing the photos on their site, I can see more why the thickness of the streaks at the sides (suggested by WILDGuides Britain's Birds) might be a good indicator, if not perfect.