Complaint about repair

My brother bought a brush cutter at Game Stores Gillwell Mall East London, when he gets home the machine was not cutting grass, he returned it to the store , they did what they did, and he returned home with the machine, when he gets home the machine again didn't work and he returned it back to the store, they booked it as a repair, and this thing happened in a period of six days.

I phoned the store for follow up , the Sales Manager phoned me and he said the machine is still with the supplier, and it's hard for them to reach the supplier for more info about the repair, coz they had to hold for a long time,

Again lastweek I sent another email for feedback, I didn't get any answer, and also they are not contacting me , it's me who has to contact them.

Tried today to send email to their head office, still no luck because now it's been so long all I want is a refund and go buy somewhere else because they don't care about their customers, their service is the poorest of them all. I will never ever buy anything from them will prefer to buy somewhere else because their services is so so POOR.

Hope this will reach them