As peri Gr5's comments below last night I opened both Gcode files in Cura and 'textedit' (word pad for Mac) and checked the all the 'pre print' Gcode. Everything was the same appeart from the speed at which it moved the print head towards the bed.
Old 14.03 file - F6000
New 15.04.05 file - F9000
Therefore I sliced another part and modified the Gcode to be F6000, however it didn't make a difference.
I then tried F5000 and surprisingly it didn't stick!! It moved towards the bed as it should however it sounded noticeably louder and it wasn't as 'smooth' as it should be.
I then tired again with F2500 and it jammed as per the original problem.
After this I uninstalled 15.04.05 and reinstalled 14.03, however now it is not working either!
There doesn't seem to be any logic to this problem