From what you have written in your post I would suggest it is most likely the accountants that have held thing up and just the general speed of underwirting an application nowadays.
Normally when an application is submitted it can take a day or so to be looked at by an underwriter, they may then apply to your accountant for a certificate of earnings, this may take another day or so to be filled in and returned, this will then join the documents queue which can take up to 2-3 days to be paired up with the application and viewed by an underwriter again. If the underwriter is happy with the application they can then instruct a valuation (if neccessary) which could take another 24 hours before they contact you.
It is easy to see how an application can take a while to go through. If I was to place a figure on how long it takes me to get my applications from application to formal mortgage offer I would say in excess of 10 days so a week for your application is still within normal timeframes.
If your wife has residency and the adviser (laugh, banks do not give advice anymore due to liabilities) took a copy of it then this will be noted by the underwirter and will not create an issue. Being on the electoral roll always helps an application but will not generally fail an application.
Hard as it is to tell yuo when you are a first time buyer, but be patient, let the banks do what they need to do, they are ging to lend you a HUGE wad of money and they want to make sure that they are happy with you as applicants before they do so.
I always laugh at first time buyers being so eager to get their mortgage and then spend the next 25 years wishing it was gone.
From what you have said I would just put it down to underwriting queues, if you passed the initial credit and affordability checks then its just a matter of being patient. If you have no answer before early next week I would give them a call and get an update. it may even be that they underwriters want some further documentation but you have not been informed (it wouldn't be the first time)