I want to use my PC for internet access in my office (shed).
Shed does not have phone line or cable points.
PC does not have wireless capability.
Moile phone can be used as Access Point (but PC can't detect it- no wireless capability)
What is the methods to provide plug-in/ bolt-on wireless capability for my PC so that it can use my mobile Access Point to connect to the internet?
Or is it going to be simpler/ more economical to purchase a Mobile Broadband USB modem?
Most the costs depend on how the data plan for your phone works and if they have a sharing plan for a new USB modem or if it is a new plan. The device costs are very much secondary. It tends to work better if you use a USB modem device for data use on a PC.
That all said.. all you need is normal (ie 802.11) USB device and let your phone be the hotspot. you can get even N based wireless adapters for less than $10.
Your phone may also run in tethered mode with a USB cable directly between the phone and the PC. Again you need to read the fine print they may charge to activate or for usage of this feature.
I have it sorted- got a USB wireless adaptor to give my pc the capacity to communicate out of its box. Now can use mobile as "hot spot/ access point" for internet browsing.
Cost was about $60 for the USB device. Phones suitable download included in package