Sounds to me like they're simply not fit for purpose, and you should be entitled to a refund or replacement. Document exactly what happened, including the broke-on-day-of-delivery bit, contact the shop, tell them what happened and what solution you want. If they aren't helpful, put it in writing, and start citing the legislation (Sale of Goods and Supply of Services Act, 1980) - see
[broken link removed]
- and explain that you want to deal with them on an amicable basis but that you'll be prepared to (/will have no choice but to) bring it to the Director of Consumer Affairs if they won't resolve it to your satisfaction.
Good luck.