Looks like Dell have an error creeping in on some sale items, Seems like around £8 being taken off many low cost items, this coupled with free delivery is making for some bargains on low cost items.
Take a browse through the different sections and sort by price low to high for best effect.
Type/Use/Compatibility : Headset - wired / PC multimedia, videoconferencing system
Included Accessories/Cables : Headset cable
Headphones/Form Factor/Impedance : Headphone - monaural / Semi-open
In-Cord Volume Control : Wired
Sound Output Mode / Response Bandwidth : Mono / 20 - 20000 Hz
Microphone / Microphone Operation Mode : Built-in - boom / Mono
Connections : Headphones