I'm currently in an argument with Michael Kors and Selfridges over the same thing with a £330 bag that I've had for 3 years, but have only effectively used for a year. MK said it was out of warranty (2years) but agreed it was faulty so offered £330 MK vouchers. As the bag itself is otherwise in excellent condition and I love the style, I've gone back to Selfridges where I'd bought it from, and asked for other a repair or my money back. I'm waiting to hear.
£330/£300 is a lot of money for a bag, and I don't think it's acceptable that such an expensive item has a useful life of only 1 year. I don't think it's fit for purpose as required under the Sale of Goods Act. Clearly although the bags themselves are good quality there was a shortcut taken on the handles, which makes them as bad as if they were poor quality overall.
In my experience if you have a reasonable case, as here, and keep on you get somewhere, and get a refund.
Your treatment contrasts with a very positive experience I had with Russell and Bromley. I had a R&B pair of shoes for six years, and had worn them quite a bit. One day when I was heading out for a meeting, the (high) heel broke. So I asked the taxi driver to take me to R&B to get a replacement. As they we so old and well used, I felt they had been fit for purpose and up just wanted another pair of shoes, but R&B didn't agree; they were mortified at the heel breaking.
The manager told me if I could prove purchase, they'd give me vouchers to the same value. I could and they did.