You will find the manual here. The radio is part of the 280 series radios, so there is a general manual on all in that series.
I think you'll think this is fantastic: http://www.giantintl.com/ContentManage/manuals/Moto/T8500%20English%20only%20June5.pdf
Tesco does not list operating manuals on their web site, so I suggest that you contact them directly by following this link:
They should be able to provide you with the needed manual.
This one should be a very close match. The T4508 is a foreign version of the T4500.
Use scanning to monitor channels for transmissions or to find someone
in your group who has accidentally changed channels.
1. Short press MENU until the "Z" appears. The current setting
On/Off will flash.
2. Press either + or – to turn On or Off.
3. Press the PTT to confirm or MENU to continue set up.
Here is a link to the manual http://www.motorola.com/mdirect/manuals/FV200_userguide.pdf