OK, thanks to all for this, some decent thought provoking discussion here.
1st, my reasoning.
Why do we buy nice cars and then leave them on the drive? Dunno but I certainly do. This is not some company car which I care little about. I spent my hard earned on this so I really don't fancy the depreciation or wear and tear that another 40K miles will do. I plan to keep the car for at least 3 years.
Yes, I do get mileage allowance of 40p / mile so probably a bit over break even point if depreciation is ignored.
Project is for approximately one year so no plans to run 2 cars indefinitely.
Safety?? I am aware of tiredeness etc but have no worries about a long commute. In the good old days before the Rozzers got a tad more interested I used to do a daytime office job and then drive gas tankers for 8 hours overnight as well. Ever since I can remember I have never slept more than 4 hours a night. Even now I hit the sack a 1-ish and get up between 5 and 5.30. So no safety worries for me there. I know when I'm tired, and when that happens I stop as soon as I can. Even 30 minutes powernap in the seat is a great refresher. Besides which I didn't marry my wife to stay in a B&B. I love my family and like to get home to them every night.
So, to the mechanical safety issues. I can only guess that a 12 year old MB in decent condition will be as safe, if not safer than a newer Ford or V....(sorry can't bring myself to repeat the V word). I NEVER skimp on servicing, NOT EVER. My life is worth more to me than a service bill. If it needs doing it gets done. No if's but's or maybe's. Just like I never buy cheap tyres. Continental, Michelin or Pirelli only for me. So, a decent W124 or W210, even a mega miler, ought to be safe if maintained properly. Even a MB from 12 years ago should be much more comfortable than a modern Ford or V.
So, the finances, well I don't really think of the overall cost but let's say 2.5K on a reasonable W124 and then 500 quid getting it serviced. 3 grand so far. Insurance is going to be around 400 quid for the year plus 200 quid for tax. £3600 so far. Now, 40K miles later is should still be sellable for 2 grand. I have left fuel out of this for now. Either I break even or I make a bit if the beater is diesel. Throw in a set of boots for good measure and an interim service or 2 for oil changes etc. Say over the year it costs me 2500 quid all in. That is a lot less than the depreciation the E500 would take and also I still have my lovely luxury car for the future.
There is also the sentiment that it took ages to find this E500. It has ALL the goodies listed except linguatronic. I "HAVE" to have an estate since I have dogs and I shoot as well. If they made an S class estate I would buy one tomorrow but they don't. The E class (which I cannot afford brand new) is usually specc'ed in a more basic way than the S. Hence my reluctance to use this one as a working hack.
I did consider having an S class as the "nice" car and an older W210 as the working hack but we also have a holiday home in mid wales. Thus I would have to have the dogs on the back seat of the S class. That would be sacrilege so the S class would never get used. If it is to be 2 cars then one is the commuter and the other does everything else.
As for changing to a 3 year old E320 diesel, that is never going to happen. As a commuting beater yes but as a personal family car then no. I had an E270 Avantgarde before this with a lot of goodies as well. It was not half the car this is to me. I just don't like diesel in a luxury car. It suits some people but I am not one of them. No criticism here, I just dislike diesel engines in luxury cars. Some of this comes from the usual disgusting mess the pumps are in when you go to fill up. All over the handle, the ground and the delivery hose - then all over my clothes and subsequently all over the interior of the car. Yeuk. (with a capital F)
So, from all the advice here it seems either a late W124 or an early W210 for me. The 190 is not likely to be available with the goodies, or in decent condition without a long search. I will know for sure about the project next week so may well be asking this forum who's got what they want to sell
My thanks to all who contributed, it was indeed a worthwhile knowledge gathering exercise for me.
Dom.
