Hi Aaron
Have you checked insurance costs? The LS400 is in a very high group. My quotes (for a second car) range from £490 to £4500!!!, based on a sub-20 year old car. From next January I would expect it to come down once the car hits 20, and becomes a classic.
If you are doing your own work, and there are plenty of helpful people, advice and tutorials on this forum, you'll save money, and avoid the risk of mechanics tinkering with what is a very specific piece of engineering.
I used to have a maserati (222SE), and whenever anything went wrong, there were very few people who could do anything with it. Which, looking back, was actually a godsend.
I've just had my newly bought LS400 serviced. Opie Oils provided me an incorrect fuel filter, which the mechanic has scratched whilst trying to fit, so thats £20 gone! I provided the mandatory 11 litres of red (pre-mixed) coolant, and he could only empty 6 litres worth. So I'm guessing that'll need re-doing (The colant fill tank has the instructions on it). I'm off to pick a part from toyota tomorrow, so will drop in and ask Lexus how much it will cost to do it again if it needs it.
If you know what you're doing, I'm guessing all of this stuff will be rather nicely avoided! A couple of hours looking through past threads will make most things quite straightforward.
I'd say a £1 car will need time and bits buying for it, there is a £2.1k Mk4 on Gumtree at the minute on Merseyside, which has been reduced, which looks superb (has the Dynamic handling pack, manifesting itself with bigger wheels and more expensive tyres) I guess that could need some £ on it, but it looks nice on the photos.
I've never driven a 430 so can't comment.