Sorry for the delay in replying - couldn't find fruit juice concentrate (don't have a Sainsbury's close by with will look in the baby section of our Tescos) so have only just made my first attempt this evening. I found something called Agave Nectar - an organic natural sweetener - they had this in Tesco, Waitrose and Holland and Barrett so presumable fairly mainstream.
My initial attempt (small quantities - made 6 bars)
90g rolled oats
70g raisins
20g sunflower oil
20g agave nectar
1 tbsp apple juice
1 tsp cocoa powder
Blitz the last 5 ingredients together (I used mini chopper bit of my hand blender) then mix with oats.
(this took a fair bit of mixing as the mixture is very solid)
Spread into the bottom of a loaf tin lined with foil and greased.
Bake in oven at 180 for approx 20-25 mins.
Allow to cool slightly and cut into fingers.
The texture came out fairly well but the flavour was a little bland - I think it needs much more cocoa so I will increase this quite a bit next time.
Will see what dd thinks of them tomorrow!