Hello Aaron,
The way you are dealing with your problems is impressive and I wish you continued success.
I have an E Class W210 Auto Estate with 210,000 miles and which has been largely trouble free and I would certainly recommend that you look for one. It must however be rust free and have a full service history preferably with a good Merc Indie. The 220 cdi is cheaper to run (than the 320 cdi ) and maintain and is largely bullet proof apart from occasional electrics..
Some other ideas re a reliable, quality run around (non Fiesta) are Honda Jazz and Toyota Corolla.
There are some excellent lease/hire deals at the moment with Lingcars.com and you might look at these.
Good luck.
Regards
John