This can be complicated, and depends to some extent on how the Official Receiver interprets his responsibility - they have a fair amount of discretion.
Any joint accounts will definitely be looked into and may well be frozen. It would be necessary to show the OR how much of the money in the joint account belonged to the bankrupt and how much to the partner - the latter's money cannot be taken in normal circumstances.
Any other accounts of the non-bankrupt partner should not normally be looked at but the OR may decide to ask to do so if his investigations make him think this is necessary (e.g. if he thinks the bankrupt may have moved money to the partner to place it beyond the reach of creditors). I am not sure whether the OR has a power to insist on seeing them, but if he asks and is refused he might draw adverse implications.
As far as income is concerned, the OR will be interested in the income of the bankrupt and possibly that of the partner. For example, if both are working but he is told that the bankrupt is paying all household expenses he will want to know why this is happening & may conclude that the expenses should be shared. This can lead to somewhat contentious problems because in principle the partner's income should not be used to pay the bankrupt's debts.
If you have a serious (and potentially expensive) problem of this kind it might be best to get advice from an Insolvency Practitioner - but you would have to pay.