Several buttons on my remote take quite a while or are erratic in function. I have changed the batteries, although other buttons function immediately so I can discount that. It is the ones I've used the most (on, guide, mute) so I imagine they've become worn.
To order a new remoteyou need the TV Faults option when dialling 150 or 0345 454 1111, but best to call at 8am to avoid call queues
You could also try the text messaging service. Just send a text with a description of new remote to 07533 051809. Your message will go into a queue and a representative will respond to you as soon as possible. It may take a few days.
You could also try clicking on Check service status further up this page, then when the page opens scroll down to the three tabs, broadband, TV and phone. Click on the TV tab, then my remote isn't working and follow the prompts.You should be able to order a replacement remote from there, although you might see an "Oops somethings gone wrong error message".
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali