Ian is correct, a small 64 GB drive for the OS would be grand, or at the very least, partition the drive they have specified. SSD's at that sort of size shouldn't be much more than £1 per GB
Hi Paul
I recently upgraded my system to an i7 3770k overclocked to 4.4 ghz with an nvidia 660TI graphics card. I am still using a SATA 2 drive for the OS and a faster SATA 3 drive for FSX and in all but the heaviest areas it will run FSX at a steady 40 FPS with quick load times. As I understand there is nothing to be gained by twin graphics SLI setups in FSX and would agree a single decent nvidia card would be the better option. Either a 660TI or a 670.
The price of SSD's is still relatively high so I would be steered towards perhaps a small SSD for the OS and a large capacity 2 or 3 TB SATA 3 drive for FS and addons. You should be able to get an i7 syetem for the quoted price. It would also be worth a look at PC Pilot as they adverstise systems aimed at running FS.
Seems high for an i5 price, like Steve said you should get an i7 for that. But then again the price would be up because its a local consultant and wants their cut... However whats their support on this as this could be a big difference from purchasing online/in store if they support it for a number of years for free/cheap?