If I was in this situation, I'd fund a new set of tyres using a credit card- I know I can pay the CC bill off the following month. I'm not prepared to compromise my/my passengers safety (and the safety of other road users) by fitting ditchfinders. If I couldn't afford a decent set of new tyres, then I would park up the IS200 and use public transport (but save up for a decent set of tyres in the meantime).
Why spend thousands of your hard earned pounds on a nice IS200, GS, LS etc only to fit cheap ditchfinders off ebay? If you can't afford to maintain an IS200, then don't own one- simples.
As said before, there are only 4 bits of rubber between you and the road- so fit the best quality tyres you can afford. I've used both budget tyres (in the past) and premium tyres and I'd go premium every time.
And yes, remounds are just as bad as budget tyres in my experience.