I feel your pain - Hope there may be something of use in the following : I have just managed to get a Certificate of Lawfulness for my caravan which I use on my land. I keep horses - It took alot but found using the following as proof to show my caravan and other structures mainly sheds had been in situ without a break for more than 10 years as required by planning enforcment - by using google earth, photos, and I had locals write letters in support with time scale of knowledge ie moving in to the village date etc, plus asked suppliers & those who had been on the land to do work for me ie topping, muck heap removal, hayman, farrier to write and confirm the caravan had been in place everytime they had visited to deliver /work & had tea! I also used suppliers invoices to prove timescale of their knowledge of my land/stables. I also offered an affidavite via my solicitor - I made a folder of evidence and presented it to Enforcement. I also kept a diary of all phone calls etc including name/time/date what was said (also went in folder) Stay strong & good Luck