Each case must be treated on its own merits and without a lot more info, which you probably wouldn't want to divulge on a public forum, then a definitive answer cannot be given.
The "topping up" of loans is quite a common scenario of course and in itself would not necessarily debar an IVA proposal. The circumstances of it and the history of it is something that would obviously be looked into though.
The repayment on any proposed IVA is worked by looking at a proper budget with a professional, and once all income and expenditure is accounted for reasonably then you have a figure that can be looked at for a possible IVA.
Accordingly, you may wish to discuss your options with a professional, and a good place to start is to visit
www.iva.com and have a good look around, talk to 2 or 3 providers and then make your own decision from there.
Regards.