Unable to start strimmer ?

I have been trying to start my Champion 2stroke strimmer all `summer` long to no avail. The grass is now up to my knees and no-one wants to try to repair it because they say spares are too difficult to obtain. Any suggestions would be gratefully recieved short of buying a new one. ( the strimmer is only 3 years old). It has always been a pig to start but now its impossible. I have tried renewing the spark plug and draining and changing the petrol.