I believe Ryan, a whole of market broker with experience in IVAs, has a contact that can assist Help to Buys .... but I am not sure if this could, or indeed, should , be done in an IVA if you are intending to be joint owners.
If you become an owner there will then be a requirement to either extend the IVA by a year or attempt to release equity if there is over £5k. It could also be argued that 50% of the deposit monies donated by the parents is yours and could be grabbed as a windfall by the IVA !
The solution, if your partner can afford it, would be for him to buy a property in his sole name and ownership.
My opinions are merely that .. opinions based on experience. Always seek professional advice.
IVA Completed 23rd July 2013 .... C.C. 10th January 2014