Help - 'Soupy' Plum Chutney!

I was give a couple of kilos of plums, so decided to make some plum chutney.  However, although I doubled the original recipe exactly (which was based on one kilo of plums), there's far too much liquid, even though I've simmered it for two hours rather than the 45 minutes stated in the recipe.  I've therefore been out and bought some more plums, but I'm not sure whether that will affect the keeping quality because the ratio of fruit to sugar and vinegar will have altered ... can anyone give me some guidance? 

Just to ask an obvious question - did you take the lid off the saucepan to boil it?
Failing that, Val will put you right I'm sure (and I would thoroughly recommend her book)

Yes, never had the lid on the pot, so hours of evaporation going on!  Anyway, I added another half kilo of plums (didn't want to add more in case it affected the keeping ratio); I also added some chopped dried apricots as I thought they'd probably soak up some of the excess, which they did.  I simmered it for a further hour and a half after which it thankfully seemed to be a more chutney-like consistency, so I've bottled it and am now crossing my fingers and hoping for the best!  If Val reads this, please could you tell me whether you generally need less vinegar/sugar when upscaling recipes?  I'm planning on doing some batch cooking for Christmas gifts, and also a local school fair.  Thanks