Ok, Let's do this bit by bit-

Lynsey01:
Do you have to repay over 3-5years or can you pay the lump sum agreed upfront? And that would be the end of it? - if this is the case am I right in thinking that it would about 25% of the amount we owe?

You make one single manageable monthly payment, based on your budget, for 3-5 years. IVA's do not guarantee to write of a % of your debts every time, any company suggesting this are misleading their customers. The IVA must be "fair" to the client AND Creditors, it's not as simple as on Monday you Owe £100k and on Tuesday it drops to £25k.

Lynsey01:
we could possible re-mortgage but we have only recently caught up with mortgage arrears and would be difficult as hubby is classed as self employed as the company have no UK office (they are German based but he does have a contract) - we could possible lend the money off a family member and look at re-mortgage in 6 months time to pay that person back - I would rather try and pay up front as if we are late paying one month can the creditors force bankruptcy? - We have a young family and a home is really important

There are lenders that will look at allowing you to re-finance. But as you will have seen in the news the sub-prime market is shrinking. The legal process to for creditors to file for Bankruptcy doesn’t start after one missed payment, they will usually try all they can to get the debt repaid. However, if you do go down the Bankruptcy road you will lose control over your assets, meaning your house may have to be sold, although this is not guaranteed.

Lynsey01:
do you have to advise your bank (even though you have no debt with them) and also your mortgage lenders that you have entered into a IVA?

No. However, if you do have any overdrafts or credit with the bank the will ALL have to go in to the IVA. An IVA is not "Fair" if includes some lenders and not others. Also, you should not have any other credit facilities whilst in an IVA.

Lynsey01:
if we do a IVA for 3- 5years and our income increases i.e. i get a job - do we have to declare this and increase payments? 

Yes. IVA's can increase and decrease during the term based on circumstances. Again, it has to be fair for any lenders involved.

Lynsey01:
if we didn't have the total money agreed upfront and paid a monthly fee - would the IVA have a charge on the property to secure the balance?

No, there is no upfront fee for an IVA. However, if there is equity in the home the IVA Company may look to release some of it to pay the lenders.

I hope this helps.

Basically IVA's are designed to stop the rot. Although at the moment Debt management is also becoming a prominent product.

Have a read of the debt section of the website; I'm sure this will help.