Do it, Rich! Avoid the 450s with Mercedes' own Petrol engines, they're lucky to get beyond 50,000 miles between rebuilds, and buy a 45bhp Diesel. Never available in a 450 with RHD, but plenty for sale over your side of the channel. Or do as I did and go for the post-'07 451, they have a longer lasting, Mitsubishi petrol or an uprated version of Merc's own Diesel as found in the early cars. They last forever as long as you don't go silly with the OBD2 adaptor, a trust plug and a certain bit of "reworked" Merc software

. stock figures are 54bhp on the 451s - in practice most seem to have been set at around 60 - and 130N/M max torque, they're safe for up to around 77bhp, even the 45bhp ones are much better at hills and motorway work then the petrols.
If you buy a petrol one and can't be arsed looking after it yourself (easy and far and away the best bet), make sure that the garage you use to look after the car replaces all six plugs at service time. Some independents lift the engine cover and only see the top row of three so assume that there are no more. Pillocks.
Early cars (450s) had a three speed gearbox with a splitter of the type found in some truck axles to create the illusion of a six-speed 'box. They're not quick at responding to the gear lever or paddles where fitted, 451s have a straight 5-speed Getrag gearbox and although it's no DSG, changes are nice and quick.
I just picked up a LHD 450 CDi to play with a couple of weeks ago, it's an ex-Spanish car with 438,000 KM on the clock that has a great engine with no DPF (only the new ones get those

) and has a 63bhp map on it. Interior is a complete toilet but that was kind of the point as I bought it so that I could restore something I know I'm able to drive once it's done, plus I can store up to five of the things on my drive. Cost me £500 with UK plates and one week's MOT. Even a really nice one only costs around £3k at that age (2002) but they're just like big Lego so buy a broken one and fix it.
Go on, you know it makes sense.
