faulty monitor not collected

I recently bought a Dell monitor. It was faulty on arrival and Dell efficiently replaced it with a working monitor. However it is six weeks since this happened and they have made no attempt to communicate with me about collection of the faulty monitor. I haven't been able to find an email address or phone number to contact them, I just keep getting told to go to the online support pages. I can't follow up the original discussion as it is regarded as a closed case. Can anyone tell me how to get in touch? I don't want to keep the faulty monitor around. I am in the United Kingdom.