As Mark mentioned - you'll struggle to find a 5DII for £1,000. The rumour mill suggests a 5DIII coming fairly soon so the MkII might come down a but in price. I wouldn't hold your breath though.
It's
almost always worth investing more in lenses than in camera bodies. The 5DMkII is a significant upgrade from the 5D (often not the case - camera upgrades are commonly more incremental). It really depends on the lens.
Canon's wideangle L series lens (the
16-35mm f/2.8 L) is about £1,100 which is £400 - £500 less than a 5DII body.