keep ignoring the letters? iv heard that they might try and take you to court or get you blacklisted whatever that means? something that stop you from getting loans in the future?

hi guys, im new to this forum. im a student and started parking on my college's car park which is only available for staff and visitors only despite there being 100's of spaces available, i parked there for a few weeks whilst i was in lessons and recieved 2 parking tickets from a private company stating i need to have a permit to park here, i dont have a permit and i saw the various signs saying DONT PARK HERE etc. but some friends told me you dont HAVE to pay them, so i just ignored them. This all happened in febuary when i was parking there and i have since parked elsewhere now after being caught by a member of staff who took my name etc. i thought i had got away with not paying the fines because it had been 3 or 4 months since i got the fines. However i have just recieved 2 letters from CAR PARK SOLUTIONS DIVISION - A S SECURI-T stating that i must pay the fines which were originally 70 pound but due to not being paid they are now 94 pounds which i find ridiculous for parking on my own college's car park. The letters state the fees have to be paid by 21st June or they will forward my file to their collection department. What does this mean? and what should i do? thanks