Half a lemon is the other classic for encouraging set - and the flavour compliments most jams.  Alternatively, consider using jam sugar, which is sugar with added pectin.  That's what I use when I'm making strawberry jam because yes, strawberries are low in pectin and so a bit challenging. 

I haven't had a jam not turn out as yet, although I've had to fiddle with them occasionally.  They've all tasted fantastic.  So don't give up!  You'll soon be turning them out without batting an eyelid!

I'm not near my recipe books at the moment, but I'll try and look out another jam recipe for you to try.  In the meantime, here's one from the uK thermomi site.  Haven't tried it myself, but haven't had one of their recipes fail on me yet

http://www.ukthermomix.com/recshow.php?rec_id=30

Tried the strawberry jam recipe from the book but very very runny and continued to 'cook' in 3 minute stints like it said and gave up after about 30 minutes - jam tastes nice but is runny like pouring sauce.  I used jam sugar with pectin.