In fairness, walk ups are not preventing you from getting the P&R service. You can still park your car and you can still get the bus. It's just impacting on the turnaround times. I understand it can be frustrating to wait. However, with an out of town stadium and 31,000 fans needing to get to...
You haven't paid for the service anymore than someone else with a ticket. There will be fans who have contributed through their ticket to the cost of running a PARK and ride service YOU use but walk or cycle to the ground.
The people liking the idea of bookable/chargeable P&Rs or those that think fans who live outside the Brighton - Falmer - Lewes trainlines will just have to get on with it. Will be the same people moaning about the empty seats and fans leaving early.