Chris,
1. LPJ and PAT are perfect for practice for the 15 in 15 mins
2. The CEBglobal tests they linked are indeed for those with access to calculators so would say they are tougher than those faced in the actual test. Practice being able to work out which is the correct answer without actually finding the full answer. PAT also has numerical and verbal reasoning that you can practice, arguably more accurate of the level actually faced.