Re the dot in the box. I found that looking at the dot and thinking "fly to the dot" made it very much easier.
For anyone using the cockpitweb software (and if you are not, you should be!), beware that the presentation of the graphics at BA is a bit different and more up to date, this can be a bit off putting if you are not expecting it. Also the "arcade flight sim" test is not included, but there are plenty of mentions of this above.
BTW, for anyone banging their heads on the radar test, FWIW I found simply reversing the instructions the easiest way and mentally plotting this on the screen (they were very strict about not using fingers on the day). Hence "10 North" becomes "10 South" and "5 North East" becomes "5 South West". It's really as easy as that. On the day, you get to see if you were right or wrong (on this test and several others also).
Another tip, already mentioned by localiser but worth repeating, is on the subtraction test, try adding the second number to the answer rather than performing the subtraction. This is faster for most people. E.g. If the question is "920 - 118 = 802" then add 118 to 802 and see if this matches the first number.
Good luck,
KT