Poundstretcher Head Office Number or Address? UK?

Last month i bought a small Halogen heater from my local pound-stretcher it was £6.99 offered two heat settings and a safety tilt switch.
I didn't have much money and putting the heating on all day was getting expensive so decided that one of these heaters would be good to just take the chill out of the air until i really had to put the heating on.

Anyway it was all fine until yesterday when my Labrador whacked it with her tail and it fell over and the safety tilt switch didn't work. It was laying face down on the carpet fully on. I stood it up straight away and tested it by leaning it back and it still didn't turn off like it is meant to in the event of it being knocked over. I rent my property and i'm lucky it didn't burn the carpet cos i would definately have lost my deposit.

I went to pound-stretcher today and manager said because i hadn't kept my receipt or the box i couldn't get it refunded or exchanged even though this is a serious health and safety hazard. I know it was only £7 but what if mine isn't the only one like it and it hurts a kid or something?

It wasn't until i got home i thought i should have asked for a Head Office number.

Anyway i can't find one. So if anyone here has it or knows of someone else i should contact then it would be much appreciated. Thank u!