OT heating flush- recovering money from installer?

June 07 I had a condensing combi fitted, on the quote it included flushing and adding inhibitor with a workmanship warranty and 2 year warranty on the boiler. Im now told by the manufacturer after a recent repair visit that the system requires further flushing or power flushing. I have approached the installer who tells me his warranty on workmanship is only 12 months and as I missed my 12 month service any further work will be chargeable.
Where do I stand on this, can I get another company in and possibly recover the cost from the original installer?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.