Parkers price guide for 2004 04 plate gives £3600 for good condition private sale.
That does seem a bit steep to me.
Best to trawl through adtrader and the locals and see what is actually being asked for them.
The asking prices are quite varied.
I think if you price it right and reasonably, it'll sell.
What Car gives £3,090 for an ELX and £2,690 for an SX as a private sale. That's with a service history etc.. Looking at the ads on Autotrader, those don't sound far off to me.