I'm not a lawyer, but did you buy it online or in person? If the former, then I would have thought you should have 14 days under the Consumer Contracts Regulations. (I see their site says "At Bass Direct, we offer a 48 hour approval period on all purchases purchased in store and 7 days for items purchased online or over the telephone. ", but I don't believe they can override statutory regs).
https://www.which.co.uk/consumer-rights/regulation/consumer-contracts-regulations