I think I know where you were , the first services after turning right off the A350 , there is the permanent take away food place in the next lay by after leaving the Esso .
£14 seems a rip off at Warminster , similar to the Swannery car park in Weymouth , with Government rules on not being allowed to stay overnight , the machine takes the money for 24 hours anyway , if you arrive at 08.30 , it’s a fiver until 15.30 , and free after 18.00 , but £8 to stay until 18.00 .
Which allows parking for 24 hours .
With the showers shut at Warminster , I wonder if the fee included use of the hose pipe outside for a military style wash ?