I did mine at the same time as Andrew above and also came in via tech cert so can't really comment on the L4. What I would say though is that I don't see how it could be any more work if you want to get it done in 2 years. I was working every minute that I could, even during my sons day time naps at the weekend. You can take up to 5 years if you want though with either. I spoke with Dave a couple of weeks ago and that is essentially why they are not delivering the qualification, they cant commit 5 years to it.
People struggled with one of two aspects of this course. Either writing at L6 or keeping up with the work. Like Andrew I thought the level was ok, the first critical evaluation was a challenge but once you have done one its ok, more of the same really and just a skill you need to learn. Getting going with the IRP was also difficult but again once you get going it just unfolds in front of you. Not quite but you know what i mean. The work load is intense though. I was told on several occasions not to underestimate it but I still did. On day one we were given 6 assignments to do in three weeks. One was to critically evaluate import controls for plants, organisations and agreements. At the time I knew nothing about the WTO or EPPO so a lot of research. I think I did 3 so was playing catch up for the whole of the first year. I made sure I stayed on top of the work in year two and this really helped. That would be my number one tip, stay on top of the work. Second would be do your re-submissions as soon as you get them back. You can knock them out in 30mins sometimes. You'll get a sheet with all the units on and the AC which you are supposed to tick. I colour coded mine. Red - not stated, amber - underway, green - done, blue - to re-sub. Sounds a bit geeky but i could see exactly where i was and what was a priority. Gives you a little bit of a boost every time you put a green box in. I found it quite motivating when i could see the whole thing turning green over time and you will need something to motivate you so if not this then something.
In terms of cost, from your posts I assume you already have a pretty good library so don't go mad. See what you really need. I think I bought about 5 books over the two years. You have to be prepared to scour the internet for free guidance though, there is a lot of info out there. You will also need access to the online journals from the AA so get that set up. There is an ISA site also that has all their papers on for free that are older than 1 year. This can help to keep the costs down. These are things you can start putting in place now. You can probably start doing your tree profiles also. The nursery/landscape unit is the same as the one on the L4 (its at L5) so not difficult but still takes time.
Hope this helps