Questions............
1) Do many (if any) people use the car park to see people off on the train and then to meet them (or anybody else) later the same day?
2) Do you need to display a ticket for the free parking period?
I know of a few cases where somebody has made use of the free parking time more than once during the day and then been sent a PCN as the ANPR recorded the start of the first visit and the exit from the subsequent visit - discarding the other exit and entry times. As no ticket was issued for the free period, it was difficult to prove.
Yes, there are plenty of drop offs and pick ups ... however, they're at the separate 20 minute drop off and pick up point at the station gate, under
GWR▸ /
APCOA▸ management and I would be surprised to see (m)any cars visiting the main car park for the purpose. With the 30 minute free parking in the main car park, I don't yet know if a ticket is needed for that period; while it is designated "for railway users only", I doubt anyone will stop there for less than an hour anyway / pay for less that 2 hours by the time they do even a short round trip on the train.