how do I start a JCB 380 circular saw?

I have owned the saw for approx 18months but only used it 3 times (approx 3hours total), I have emptied the old petrol and replaced it with new mixed on 30/1 unleaded and 2stroke oil.
The saw was working great yesterday but this morning I can't start it, I have taken the spark plug out and it seems fine apart from it being wet, I dried it off, checked for a spark - sparked OK, popped the plug back, locked the handle rev trigger, pulled out the choke, switched it on then pulled about 20 times till my arm ached - it turns over but won't start, I repeated the above, still can't get it to start....I'd appreciate any advice