Loads of choice at or just under £5k - I'm a bit old fashioned and use Autotrader almost exclusively (but do dip in and out of eBay occasionally).

For your requirements, top of my shortlist would be a Skoda Octavia Estate 2.0 diesel (I'd go manual not DSG).
Should be able to get something 10-12 years old, with plenty of life left in it - though won't be ULEZ unless you want to focus on only the petrol models.