Thanks to everyone for their comments, it has helped me a great deal over the past months and I thought it was about time I contributed!
There was no mention of a 7,200rpm drive on the Dell UK online system customiser, so I rang up Dell and they said all the drives are the 4,000rpm-ish type.
I'm glad I rung them though, because I got another £50 off for no reason.
I have got to wait until 2nd February for delivery, 1 day before my 21st Birthday.
I'll take some nice pics when it finally gets here!