If you’re going the banger route, buy privately. If you go through a garage there needs to be a near £1000 mark-up to justify their costs in selling it. And if they’re selling it for £1000, well....
I’m with Shandon Par. If it’s for work you need something utterly dependable. One day’s wage a month goes towards the car payment. If anything goes wrong with your banger, which it will, regularly, you’ll rarely get it back from the garage with it having cost less to fix. And then you’ve got consumables like tyres etc. Financially, the £99 Corsa wins hands down IMO.