Your credit score means nothing really and lenders don't even see it. They go on credit history and, with the IVA still showing, it is pretty much shot. Your partners file will look a little healthier due to ongoing accounts, but, with the IVA showing, can still be considered shot.
Store card accounts aren't really looked on as a bonus in a credit history and utilities, phone contracts etc are better, long term.
Some posters here expound that the likes of Marble, Aqua and Vanquis could also be viewed with suspicion. However these cards are not just issued for bad credit applicants, but also for those with not much, or no, credit history, for whatever reason.
Have a read here:
http://debtcamel.co.uk/repair-credit-record-iva/
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014