Builders warehouse refusing to give me refund

Builders warehouse refusing to give me refund. Do not purchase from builders warehouse I bought a high pressure hose (karcher) from them but it was not up to standard when I returned it they said it had to go to the manufacturer for assessment after more than a month they said I should collect it. So now I am being forced to take the product when all I wanted was a refund I am not happy with the product and do not want it. Builders warehouse say they are only the middle man and it's only the manufacturer who can authorize a refund how is that my problem. I did not purchase from karcher I purchased from builders but they can't even authorize a refund how pathetic