Jonny, you don't say if your new greenhouse has any gutters. Mine has, so i've put a short length of hosepipe from one end into a cheap Wickes plastic dusbin and blocked the other end off. If it dosn't have end fittings, then a cheap small funnell (like they use for winemaking) placed under the end will collect most of the water. If it works, you can do the same on the other side and run the pipe across the back. Hope this makes sense. Regards TC :)
