Don’t have a resin printer? You may buy the model kit at N'Tastic Scale Models:
https://www.coppermineminiatures.co.uk/product-page/n-gauge-vehicles-1926-thornycroft-pb-milk-platform-x-3-versions

Collect & Delivery – Milk transport add-on for my Thornycroft PB-type model.

Collecting milk was one of the most important daily work of railroad companies. The milk churns were collected at different farms and broad to depots, where they were delivered either directly in ventilated wagons or in special milk tank wagons to diaries or larger cities. There were special daily milk express trains, or some wagons ran as part of a passenger train.

This will probably be the last body version of my PB-type, other trucks are in work. But I found the crane lever interesting enough to make this version as well. Chassis/cab/wheels and driver figures of any version can be downloaded here:
https://www.printables.com/de/model/302154-oit-thornycroft-pb-type-1-148
https://www.printables.com/de/model/302164-cd-more-thornycroft-pb-versions-1-148

If you like more different milk churns, you may use also the ones created Enely:
https://www.printables.com/de/model/19466-milk-churn-stand-187-h0-scale/comments/645666

There are plenty of pictures showing, that milk churns of different size and style were used within the collect & delivery service of British railways.

I had my fun creating this model, hope it will be helpful to someone for his model railway or just for display. I would be happy to see your version.

All models sized for British n-scale (1:148). Conversion values:

Continental N-scale, 1:160 -> 92.5%
TT-gauge, 1:120 -> 123%
HO/H0-gauge, 1:87 -> 170%
OO/00-gauge, 1:76 -> 195%
S-gauge, 1:64 -> 231%
O-gauge, 1:48 -> 308%

Update 2024-07-11:
In RMweb-forum I got advice, that the floor planking of platforms/bodies should rather be longitudinal, than transversal. Earnestly I don’t have photographs showing this area, but there are good arguments that the longitudinal planking is more likely. By that reason I created modified platforms/bodies marked as “Rev1”. Your choice.