Good advice @Unclebob
Just a point but I do not believe Grants will fund a nearly new WAV, I may be wrong. They will look to fund a new vehicle. The first step is to talk to Grants, the second is to call Allied Mobility and arrange a home demonstration if you feel the Tourneo Custom Independence (as it it trademarked to Allied) is the right vehicle for you. The demonstrators themselves are a huge source of information and advice and once the grants process is underway they feedback and advise the Grants team over the best vehicle for your son.
There are many other Converters that can provide demonstrations, McElmeel have a growing reputation, they are Northen Ireland based but will demonstrate all over the UK.