The MK5 1.9tdi's (105ps) we used to have at my last workplace took some serious pain and kept going and going, and going...
They all did over 140,000 miles and drove like they didn't need anything in return. They move adequately if you give it death and the ones we had did 55mpg driven hard, 70mpg on a run was possible with a steady foot and unloaded car.
You must be able to get one of those for around £4k with reasonable mileage these days? (not checked myself)