Downsides to challenging a bus lane parking ticket?

other than the time for a trial, are there any downsides or risks to challenging a parking ticket? I got a bus lane violation ticket on Preston while parked close to Lovegrove. The car was nowhere near the clearly-marked Charles intersection, but I didn't see that the whole block is a bus lane for some reason (??). So, I'd plead guilty but would ask for leniency since when I parked, there were cars parked behind and in front of me (which of course I don't have photos of). Is there any chance this will end up costing me more? $252 is already a ton.