Wireless operated keyboard and mouse sets can be had for around £20 upwards; however the operating range is not that exceptional and it would depend on just how far they are from the system and the transmitter link.
There is a limit on USB lead length, but I am not sure what it is. For keyboard and monitor, you can get so called KVM switch sort of things. Try ebuyer.com, you may find some there. By the way they also have usb extension lead.
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