I have the TC215/B with 6 sensors ... but 4 sensor sets are available ... https://www.tyrepal.co.uk/product-category/product/
User manual here : https://www.tyrepal.co.uk/wp-content/uploads/2017/06/TC215B-user-manual-contents-20160222.pdf
that 4 tyre set is what Mrs Builders astra estate has fitted
hers was branded DUNLOP (the tyre company)
same sets on ebay ,non branded, for sub £20 delivered
sometimes have to plug the display in to charge (via USB lead from the stereo) as the unit doesn't get much sun where she parks at work
but the batteries are easy to change in the valve cap sensors
internal battery is IIRC a small 3.7v lithium ion that could be swapped for bigger.
the display unit screen goes to sleep unless movement is detected ,to save battery life
not sure how accurate the tyre temperature readings are , but the PSI or BAR (you can choose either) is pretty accurate
the only thing i would say is the sensor valve caps are big ,so......
not a great item for someone who stuffs their N/S tyre wall into the kerb every time they park
as it is a completely aftermarket ,independent system from the car , not an MOT item
though if its bleeping, chances are, they tyres need air ,which is an MOT item