what he said, and remember you won't get your postage back either, so you get back 85% of the product cost, e.g product £100 plus £10 shipping, you will get a refund of £85 (£100-£15 restocking fee).
It's to cover the administrative expenses of returns of unwanted goods as we all want our original purchases to be as low as possible, there is no spare profit padding in there to run the refunds as complimentary, you pay for use of the return service now.
1st Class Recorded is insured by default to £28, so depending on the value of the product that may be adequate insurance.
If it does not work properly and you have not had it long you may be able to reject it under the distance selling regulations.
http://www.hmso.gov.uk/si/si2000/20002334.htm