I bought a rollator online from Co-operative Independent Living.
The brakes broke after about 18 months. The rollator was guaranteed for 12 months but the brakes are guaranteed for 3 years. When I spoke to the Co-op they wanted me to return the rollator (by courier which they would organise), I explained that I could not manage without the rollator so they sent me a replacement one.
I was really pleased by the customer service offered by this company.