Another chap on here flew a PA28 into Gatwick last year - cost him about £860 in handling fees, landing fees, parking fees for 3 hours!
Indeed,
.
They later refunded half that...they'd accidentally charged me the 'summer' rate rather than the 'winter' rate', but it was still on awful lot...and not something I'd do again in a hurry. I may have been lucky with the time of day (aprox. 1100) but I came away suprised at just how easy and painless the whole thing had been; ATC were great, the handling agent was friendly and helpful and the traffic wasn't too heavy either.
My inspiration had been seeing a Seneca in the take-off queue at JFK while coming back from a holiday last year...I know people like bose have been to Gatwick many times but I actually thought it quite a big 'thing' at the time. The reality was that it was a piece of cake though...just make sure your RT is slick.