You file a claim in the small claims track (via money claim online) against British Waterways. They are liable for its bailiffs. DO NOT contact the bailiffs or let them know you are taking their client to court. Use
this template.
Tactically its easier to claim from the authority because their legal departments usually have newly qualified inexperienced solicitors & low paid para-legals. Bailiffs and their insurers usually employ top-notch city lawyers to represent them making the authority an easier target in the county court, plus its easy for the authority to reclaim it from their baliffs - or take away their contract!
If you are complaing about an HCEO then these are directed to the Ministry of Justice as they are authorised by the Lord Chancellor. I am waiting on info from MofJ about a complaints procedure for HCEO's & I'll post a template.