TB is right on the KA's ball joints rust and sills same for fiesta's
DCi clits are very good £30 road tax and a very reliable common rail engine theyre cheapish now especially high mileage variants
Steer clear of TDCi 1.4-1.8 ford engines friends have had loadsa trouble with them!
Peugeot/Citroen vehicles with a rear torsion beam suspension (106,206,306,Xsara,Saxo) should also be avoided at all costs the back axle can and does fall off!!! the subframe mounts go and thats game over!
Go Japanese micra's are bullet proof!!!! all that goes wrong with them is front cross member rusts away and is simple to replace or usually weldable!
Corsa's aint too bad avoid the 3 cylinder one iirc its troublesome? all corsa's seem to suffer is rust especially around the drivers seat area!!
ive had a 1.4 rover 400 was a very good car!! we kept it 2 years did about 40k miles in it! what killed it was rust the sills were rotten
your best bet is the 6N1 Polo theyre tough! and reliable! 1.4 8V is the best one imho gearboxes are theyre only downfall so make sure your happy with it on the test drive