Ordered items online and haven't received them............?

i ordered 2 items online from top shop 6 weeks ago. they said delivery would be In 7-10 days. exactly 3 weeks later i emailed them and they said to check with my local post office. 1 week later i emailed again to ask for they items to be refunded as they still had not arrived and they said they were investigating the matter. 2 weeks after that i emailed them again to reiterate i wanted a refund and they are saying the courier they use said that the items have been delivered but i still have not got them. all i want now is my money back. does anyone know where i go from here????