Generally, from my experience most contracts with the main Self Storage company’s in this country will have a point in their terms and conditions stating that if payment on the rental goes unpaid for 90 days, they have the right to enter the unit and will instruct bailiff's to enter the unit to remove the goods.
During the 90 days, they should try and contact the customer on multiple occasions to make a payment and can sometimes offer a lower settlement offer so that the goods can be removed.
They should also send up to 3 letters stating the signed terms and conditions and advising the customer what could happen to their goods should full payment not be received. These are usually sent via recorded delivery.
If after 90 days baliffs are called in, depending on the value of what’s inside, it will be either sold at a public auction to try and recoup the outstanding rental fees or dispose of the goods it they have no commercial value.
If the goods are sold and the money received doesn’t cover the outstanding rental fees, some companies then pass they remaining outstanding arrears to a 3rd debt collection company.
There has been a few instances were some people have tried to take company’s to court, however in the cases I’ve seen it didn’t go in their favour as long as the storage operator followed their terms of the contract and have a signed rental agreement from the customer
Each company have there own set of terms but generally it will follow their above process.
Hope that helps
