janerowena I'm intrigued by your longhandled perforated diffuser underthingy which stops jam from burning. PLEASE would you tell us the real name of it? I want one! 
DH and I regularly make jam, mainly from foraged fruits or our own home-grown stuff. We have a maslin pan and burning wasn't a problem till recently, when DH tried to cook some plums straight from the freezer and didn't realise there was a thick layer of burnt gunge at the bottom of the pan.
We saved most of the jam by decanting it all, picking out the burnt bits, scouring the pan (accompanied by much cursing and muttering from me in the process) and continuing. Luckily we got away with it!
I find that a jam thermometer doesn't often reach the correct temperature - or alternatively, it does, but it's still not passing the wrinkle test. It's a tricky one - I often find it difficult to tell, and we've had some thick jams and some a bit runny but none overly so. It's good to know we aren't the only ones having problems deciding!
We never add pectin or use jam sugar, just ordinary sugar - but we do use crab apples in varying amounts with the fruits with low pectin. We also make careful notes for each batch, of the amounts of sugar, water added, and which fruits were used. None of our jam has ever gone mouldy - possibly because we tend to cook it a bit on the long side, in order to be sure it's reached setting point!
Because we don't buy fruit to make jam, the varieties are limited to plum, hedgerow (containing varying amounts of blackberry, sloe, crab apple, rowanberry, hawthorn berry and elderberry), bramble seedless, damson (from foraged damsons) and bullace. We make jellies, too: crab apple, sloe and crab apple, rowanberry, japonica - and last year, redcurrant because Mr H got a load cheap from a market.
I'd like to try making fruit butters, fruit cheese and leathers sometime. Anyone had experience of making these?