I can give you a few 'low-downs' on the Ka.
On the plus side, they handle very well, with a bit of lift-off oversteer available, and they are fairly comfortable over a longer journey. No cambelts to worry about, either.
There are a couple of versions;
The early (pre 2003 Endura-E 59bhp pushrod engined model)
The later (2003-MY onwards Duratec 68bhp engine).
The lower-powered engine, although economical is a bit of a slug, holding 70mph is a mission.They are also known for the spark plugs overheating and sticking in the bores (head removal job). TPS fault causes the revs to hang-up and water ingress can cause the central locking and electric windows to fail.
The later model doesn't have these issues.
Common faults to both though, is rust - floorpan, rear hatch (around the wiper), filler cap area all rot from the inside out. Exterior door handles can snap their linkage - both mine did.
Also, due to the lack of side protection, they dent easily.
Something I didn't like on mine was the lack of an engine temp gauge - had a thermostat fault on mine which could've taken the engine out.
The rear is VERY cramped, and only has 2 seats, boot is tiny.
Overall, it was a good car when new, but I think it has aged pretty badly - the tin-worm weakness would rule it out for me (mine was starting to have issues after 3.5 years - here's to one more than 3 times that age would be like.
How about a Yaris/Jazz/Sirion/YRV - these seem pretty unburstable?