Ok, so this evening I've tested the apple/blackberry that I might be having problems with. The DJ that I actually racked last week is still giving me a gravity reading of 1050 (it was topped up with cheapo supermarket apple juice to remove nearly all the air space from the racking).
The other DJ that wasn't racked last week now shows 1030 with might be a 5 point drop or thereabouts from last weeks reading.
Like an idiot I didn't note down the actual readings. Both are still producing bubbles at the valve, but they still might have stuck and are just "de-gassing". So I've mixed 1 teaspoon of Tronozymol yeast nutrient into 20ml's of water and added 10 ml's to each of the DJ's and given them a gentle stir.
Hence if it does turn out that they're not stuck it won't matter, or if they are, then the nutrient will help towards a restart procedure.
I'll test them again next week, if the gravity has dropped then I'll leave them alone, if it looks like they're stuck I'll put them together into a 2 gallon bucket and do a restart. Though I'm thinking that I'll probably also test the pH just in case it's a bit too low and it's affecting the yeast. I can always add a bit of gypsum which should help bring the pH up a bit.
I'll have to wait and see.