You must take reasonable care of the product so if you return it faulty under the DSR without telling them then it gives the retailer reason not to refund it. As it says in the article, you need to return it under the SOGA which gives you additional rights.I don't think that's the case as you have to have a reasonable opportunity to test? http://whatconsumer.co.uk/returns-and-refunds/
Still, good service to accept return without quibbling (as a lot of other online retailers tend to).