dodger12 - PCN from smart parking

hi, can anyone please advise, I received a pcn from smart parking for overstaying on asda store brighton, the date of contravention was 7/4/2015, I received letter in the post on 18/4/2015, I had disabled badges in the window there were no notices to say I couldn't park or stay there for any length of time, I know im allowed to park on double yellows for 3hrs with disabled badges, it show my vehicle entering site at 11.15.43 & vehicle exiting site at 15.23.18, on the letter it says £40 must be paid within 14 days & as I only received the letter in the post on 18/4/2015 that is giving me 3 days notice before the charge goes to £70 could you please advise me on who these smart parking people are & how I stand with this pcn... regards dodger12

dodger12 - PCN from smart parking