Tried some Envelop XXX's and they're measuring at over 2400Ah each which is good news. The display reverts to 2.4aH as opposed to 2400mAh. It seems I may have a duff in the new set of batteries. Shall be putting another lot of 7DS 2900's in to see the result.
So far the charger seems a worthwhile addition and much better than the previous Vapex one. £20 well spent!