The Hot House programme, which was named as best wholesale business initiative at the recent Top Shop awards, offers retailers impartial advice on store re-fits, range, layout, merchandising, pricing and technology. It aims to convert a further 1,500 stores by 2010.
Landmark managing director Martin Williams said: "I'm delighted to have joined ACS and feel that our retailers will benefit from the strength, knowledge and services of the association. We share ACS' vision for a vibrant independent sector and we look forward to playing an active role within ACS."
ACS chief executive James Lowman added: " ACS is proud to represent Hot House and we will be strengthened in our fight for independent retailers."