Welcome Lez,
Personally i wouldn't buy that PC for PC World.
You got a few choices, build it yourself, buy off the shelf or spec one on a website and get them to build it.
If you build it your self you will need to buy all the components fit them install the OS and troubleshoot it if it don't work first time.
If you buy off the shelf you wont have much if any choice as to the quality of components.
If you spec one from say
PCSpecialist or
Cyberpowersystem then you get the choice of what you want with the bonus of someone building and installing everything. But you may spend slightly more if you do this, but you will have a pc thats ready to go out the box.
Aside from the above also have a look at...
3BSystems - I have bought a pc from them before, the spec isn't set in stone so you could add/takeaway components to suit your needs. best bet is to give them a ring.
Hope that helps.