You can pre-order the Nintendo 3DS for £199.85 at Zavvi now, and both colours are available at this price. In the email I got, it advertised still getting a free case. But as confirmed by another user, they have none of those left.
2% Quidco or Maximiles (iPoints) also available ordering through Zavvi. Your card does not get charged immediately for orders at Zavvi, nothing is taken out until the item is dispatched.
Unfortunately a lot of the latest vouchers for Zavvi state that consoles are excluded, so I don't think you'll find any that work. *UPDATE* I just tried the £6 off £60 voucher code (QUIDSIX), and it actually worked. Despite saying that consoles and electronics are excluded, the price reduction was applied. So you can pre-order for £193.85! I don't know if this is an error which may soon be fixed though, so you should probably try while you can. The voucher runs out at the end of this month.
Still, with or without, it's a great price from a great retailer. I hope you liked my first post.