Without sounding arrogant, I have to agree with Steve - the tests are hard for a reason.
I'm only in week 3 of training, but there's no doubt that it's hard bloody work alright.
Not just THE content (everyone can learn stuff) but the AMOUNT of content and the depth to which you need to know it, could be quite overwhelming if you don't have an inbuilt solid base to start with.
The online tests are repeated at the Assessment day - some say they're harder, I thought they were easier because I didn't have a calculator for the online tests - but they are much of same only more and at a faster pace.
Personally I'd find it hard if I waited a year, got through the online testing then didn't make it through the assessment - but that's just my two cents worth, take it for what it is, and good luck with whatever you decide.
How's the weather up there Steve?!