Stan is seems as though they are a legitimate firm but nevertheless I am sure they are not allowed to harrass people as you are describing, maybe a call to the Law Society to complain might help. Found the following on line:

Locksley Law is a legitimate UK-based law firm, trading as RH Law Ltd, specializing in consumer rights, particularly claims for mis-sold PCP (Personal Contract Purchase) and HP (Hire Purchase) car finance. Based in Manchester and regulated by the Solicitors Regulation Authority (SRA), they operate on a "no-win, no-fee" basis.