Hi Autobahn,
I do understand your despair. Your lexus dealer has treated you like ****. You've heard all these good things about lexus dealers being great and you never saw it coming.
It's all been a bit harsh. Let me say some things though.
Your car has presumable had a couple of owners, the first one being Lexus GB, who then sold it on to someone who kept it for a few years and didn't bother getting it serviced. If it had been serviced by any lexus dealer then it would have been plugged into the lexus system (and all the details of everything uploaded to lexus, including how nicely the car has been driven) and this would have been available to all lexus dealers including the one near London you bought the car from. It was therefore 13000 miles late for a major service.
Your car won't be significantly worse for this, though the oil will have lost some of its protective qualities in that time. The car will be fine, and could end up covering over 200,000 miles before the grim reaper comes for it.
It looks like a great car. It has the jewel in Lexus's crown, which few other 430's have, which is adaptive cruise control, which will seriously improve the quality of your life. It's a good colour, and the lighter coloured leather will be great in the summer months. You can have many years of pleasure driving round in what is a brilliant car. Be grateful for it. You've perhaps paid a little too much for this car - about 2k or so... but its got a lexus warranty, and its basically great. Lexus do build excellent cars.
The sales person at your lexus dealer - this is no surprise. As a general rule of thumb, believe nothing they say. Anything they say is either something they hope you'll pick up on for later, or it's something they are saying to make you want to buy a car, or feel good about doing so. Nothing they say can be trusted. This, sadly, is true of all sales people. Even buying a book in a bookshop, the point of sale person will tell you they've read the book, and it's great. They won't have. I've had lexus sales people lie and lie and lie and lie. They are the worst.
If you have a problem with itself, then tough. Lexus in Japan build really great cars, but unfortunately they have three layers underneath, and its really hard to penetrate those layers and make anyone car. Complaining is useless. When you own a lexus you have to put up with that.
There's no point in moaning, and no point in trying to dump the car. Get some serous long journeys done. Go up to Scotland, and see the Isle of Skye. Drive across Ireland, to the west coast (they have some top motorways now). Take the ferry down to santander, and drive down to Malaga, and the rest of the spanish coast. Enjoy the car. It really will be one of the best cars you ever have.