We had a look at 2007 C Class 2litre diesel today. 75k - girlfriend liked it and seems like a different league of car to her Modus.
This feels like about the worst car you could spend £4-5k on. It's likely to be a bottom of the market example at that price and is likely to be quite troublesome.
Lexus. Go look at a petrol IS250. If you're only doing short distances, the fuel consumption is less important than avoiding bills from clogged up DPFs.