As time is really against me at this point, I decided to investigate the UDK's Speedtree tree model generator to make trees for the in-game environment. Whether these will be kept in will depend on the time I have left and the opinion of the Tutors when I go back to university next week.
Anyway, Speedtree is a little complicated but a few handy tutorials online such as this allowed me to get to grips with it without a lot of hassle. I've made a few custom trees to go in-game in an attempt to boost my enthusiasm with the project - creating the terrain has become a laborious task and i'm sick of it at the moment.
Some of my trees didn't work initially - the ones without leaves. The Level of Detail (LOD) was drawing them as flat coloured squares from a distance, and this was noticable in game. I thought it might be that Speedtree requires every tree to have leaves, but upon further investigation that was not the case.
I did solve the issue quite quickly (thankfully) - to stop this happening, all I had to do was to uncheck the 'Use Billboards' tickbox in each 'bare' tree's properties. Problem solved!
Now back to the terrain editing...