Just like to post this here :) seeing as my mum is after one, thought i would share it, its designed around web surfing and office applications.
AMD A6-5300 3.6Ghz Socket FM2 Dual Core
Gigabyte F2A55M-DS2 FM2 Motherboard
Kingston HyperX 4GB 1600Mhz RAM
Sandisk Pulse 2.5" SSD 128GB
AvP Defender 100 Black Mini Tower
BE Quiet SFX 350W PSU
(Optional - Windows 8 64Bit OEM)
Total in UK was 247.91 without Windows 8, With its £317.87.
Parts are possibly cheaper from somewhere like newegg or NCIX.
I decided also not to include a optical drive due to her always using flash drives, and ill use USB for windows install.
Laters people!
I stuck with your main idea, but I upgraded a few things.
http://uk.pcpartpicker.com/p/1C6De
I changed the SSD, because Samsung makes much better SSD's.
I changed the motherboard and case so your mother will have USB 3.0 on the front and back of the PC. I also think this case is MUCH better. (Since she uses flash drives a lot, USB 3.0 is a lot faster.)
The ram is just the cheapest I found that was of acceptable quality.
The power supply is just a little more, but I like corsair, and this model is modular which means less mess in the case.
Hmm yeah the case and SSD are better, but the power supply does well for the setup as there will more than likely not be updated with a GPU and if ever need be I can swap the CPU and just update BIOS and Gigabyte seem to have the best support for older models, but I may go with your build :)
Whether its gigabyte or not, I would strongly recommend a board with usb on the back and internal connection. I use my adata usb 3.0 stick for work all the time. I teach english so I have to transfer video files and etc frequently. It really is a lot faster and saves a lot of time over usb 2.0.
Also, Asrock makes great boards. I am on my second right now and I am very pleased with both. My last one was an AMD and my current is an intel based board. Both have worked extremely well.