Low emissions zone extortion

[Gov atm]

Hello there, i am after some advise as to what i can do about an unfair situation, i had recently started a new job in essex and had to use my van to visit a couple of sites just within the m25 area its the first time id driven near london as i avoid it like the plague, i have a reliable old transit as more modern vans id had always used to let me down, now allegedly id driven into a low emission zone and after about a month had a letter thru the post saying i owe them £750 then a week later another letter for the same amount so £1400 in total, i was in shock as had no idea what this was about! When i phoned upthe person was very un helpful, i said i had no idea my van wasnt allowed in that area, and why wasnt i given a warning letter to say i couldnt drive in there? and she just said we exspect people to know! I asked why they think i owe £1400, she said i obviously hadnt recieved the 1st letter to either fine (very convenient to them as it turns out you cant appeal after 28 days of the 1st letter and as they hadnt sent them to me i was unable to appeal and owe the money!) Bailiff turned up and i have had to take out a loan to pay him before he took all my possession! Now i have been back up there to the area and the signs say nothing about a charge, nothing about visiting a website to check if a vehicle is liable for a charge, when or how a charge is to be paid and the signs are at a low height so if you are in the middle lane and large vehicles are either side of you they can be easily missed as there are very few signs and the low emissions sign has a hgv safe area sign under it implying its somthing to do with lorrys! And i have a feeling they have done theses signs on purpose, any asvise on how to handle this would be greatly appreciated as have a wife with a medical condition and can ill afford this sort of money