An attachment of Earnings order is made by the county court and are governed by the Attachment of Earnings Act 1971 there are two major disadvantages, apart from the one you are concerned over. Firstly it reduces your flexibility to manage your own affairs and secondly it notifies your employer of the debt, some companies in the security, financial or other fields have written as an express term in the contract of employment that if an attachment to earnings is applied this will be considered gross misconduct and could lead to dismissal.
Hopefully you are not in this position.