Hey,
I’m looking to do a full upgrade of my PC.
Processor - AMD Phenom X4 2.6 Ghz
Graphics Card - Something like - Radeon HD 3850 512MB
RAM - Corsair 4 GB
What mobo would suit, something quite decent?
Cheers and Merry Christmas!
Welcome to HWF 
I would suggest the MSI K9A2 CF-F as a motherboard. It costs somewhere between $100 and $120. It supports your processor, the graphics card that you suggest, and up to 8 GB of RAM.
But as a piece of advice, stay away of the ASRock motherboards, as they are worthless in the low pricing ranges…