First things first i am 19 years of age
Secondly, what are you using this machine for? If its for gaming or heavy duty tasks like video editing then its certainly a good machine (there is no doubt this is a powerful PC in my mind), you're gonna be able to play games on that for a while. If however its for just surfing the net, word processing etc its a bit overpowered (you could get a cheaper PC for those tasks thus saving you £££).
It is a good machine though but i'm honestly not sure on the price, having never bought a pre-built PC before i cant comment on the price, it might
be a bit over-priced but i'm not sure (MicroBell seems to think so and he seems to be the learned one round here
), having seen the specs it might be OK. Try researching on the internet for prices of similarly spec'd machines to see what you can get for your money elsewhere. I'm tempted to say its an OK deal but i don't have enough experince of pre-built PC's, you could try PM'ing one of the people who replied earlier letting them know you have listed full specs so they might be able to give a better estimate of value for money.
The thing is, everything listed on the PC specs look OK but they might cut corners by for example using generic RAM (not good) and poor design features (you cant see inside the case, it might be very cramped with no air-flow), they might cut corners on heatsinks, cooling etc. It seems all the 5.25" bays are taken up (although they are taken up by some impressive sounding optical drives), the motherboard says "Targa edition" this suggests it might be a cut down and generally poorer version of the motherboard.
Have you tried combing the net for reviews of TARGA PCs? Thats worth doing.