As long as the lump sum is from third party funds, which would be best, or legitimately saved from your allowances or share of overtime etc. there would be no problem.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014
My husband took a 4 month payment break - just before end of second year - and we have decided to save as much as possible over next 3 years to repay "arrears" rather than extend it as he is likely to have to extend anyway due to equity. IP has confirmed this is fine.