Hi there,
Just got my news yesterday - I have passed and as well a few tips from me:
First of all I did not have such terrific results in my CBT as other guys did and I can say that it does help to practice double what you think sufficient. In contrary to what the instructions say, practicing the same CBT module over and over again (many times a day) really does slowly improve your results (especially with things like OWT, KRN etc)
OWT: Practice over and over again at level 1 so that you can tell the digit in question by seeing the opposite, adjacent or 90 degrees digit. Draw yourself a digits circle to study the opposites (i.e. 1 is opposite to 5, 2 to 6, 3 to 7, 4 to 8) After a while it will be enough for you to see the instrument and you'll "know" the missing digit instantly.
KRN: Do practice the tasks acoustically. I found the Sky Test software really good for that. Do practice at level 3, because that is more or less the realistic speed - the math is not that hard but the time is very limited during the test.
For KRN you will get only 10 problems to solve visually (like in the CBT) and 10 problems to solve acoustically. Also do memorize the cubes of 1...10 (i.e. 1 8 27 64 125 216 343 512 729 1000) - you'll have at least 2 problems like that and that's 10% of your score!
VLR and ROT: practice a lot at level 1 and 2 until you are able to do it with 100% accuracy. Build up the speed only after that.
VMC: do practice but expect totally different figures during the test. If you practice too much you'll get used to the ones of CBT and might not be ready for the surprise
SKT: quite straightforward but learn to work as fast as you can (this is what graded at the test)
RMS: it works to group the digits in triples but do not make the mistake I was making in the beginning - trying to repeat them to yourself - you'll do more damage by distracting yourself than good
All in all I think the personality, CRM and written questions you have to give to DLR play important role as well.
And did I mention that you should practice the CBT A LOT?
Good luck!