There's no specific answer to be honest. Your score should improve when the IVA falls off however, the fact that you won't have had any new credit in the last 5 or 6 years may well mean that you have quite a low score due to that.
For us when we are looking at Mortgages the actual score isn't too important the most important thing is that all your credit reports are clear.
Regards
Ryan Radford
IVA Mortgage Expert
Zebra Money Centre
IVA Mortgage advice needed? Looking at Right to Buy and completed IVA still on credit files ?
The key to improving your credit report will be 1) Making sure that no defaults etc. for debts included in your IVA POST-DATE your IVA (that way the will also fall off automatically), 2) Check that you are on the voter's roll, 3) Obtain a credit card and use it for everyday purchases BUT MAKE SURE YOU SETTLE EVERY MONTH. As Ryan says, the score provided by the credit reference agencies is only a guide however. Lenders all have their own various ways of assessing whether they should lend.
Specialist Mortgage Advisers. Highly Commended at the British Mortgage Awards.