Well I started the bike for the first time this year and the good news is that it started almost straight away, about 5th kick, which I was really surprised about as we’ve had a cold winter. 
I then went in to get my kit on to take it out, when I kicked it over the kickstart kicked back which it’s never done before and settled with it facing the front wheel. 
I managed to pull it back but now when I kick it over it won’t return therefore I think it’s either snapped or dislodged the spring. 
To replace the spring do I need to split the engine? If I do then I may as well carry on to a rebuild. 

Not sure what model of bike but its a sure bet that you're going to have to go in there & hope the damage isn't as bad as i'm thinking. Also wildly guessing its broken the flywheel key causing the kickback. I really hope its your lucky day.

Steve, if it were me, I’d drain the oil and take off the clutch cover and take a look in there.
You won’t need to disconnect the oil pump, just move the cover to the left and tie it up out of the way.
There is a screw next to the oil pump (take the oil pump cover off and you’ll see it) which is easily missed when taking off the clutch cover. Kickstart and spring is all contained outside of the gearbox.
Good luck.

Thanks guys, I get the new workshop finished next month so I’ll get it in and stripped down. 

Make sure you use the heel of your Boot to kick it over, if you use the arch of your foot you'll feel it more if it kicks back, so I've been told