I have not come across the company before but they seem to have good reviews. UKGC reviews. As for the PC I notice that it does not come with a operating system which will add another £70. But it is certainly not a bad PC. It will certainly tan the sides of your present PC.
Have found this Chillblast which has a better CPU and a better graphics card and it comes with Windows 7 installed. Now I would probably stick it in a better looking case which you can do by clicking on the green customize button and picking one that you fancy, you will see what extra you will have to pay in red.
Sorry it has taken so long to get back to you.In answer to your question about whether this Longbow is better or not than the Fusion Elixer then I would say they are much the same. I prefer the one I linked to purely because my last build has the same motherboard and CPU and I am very happy with it.