My impression was that Bannon was on one of his do-ups with a client couple on limited funds and he sort of priced in as part of the project budget money them receiving one of these regen grants - which were then anticipated to come in soon rather than being then extant.
When he said this there was a sense of the couple getting the house paid for by the seat of their trousers rather than by savings and mortgage plus insulation grant.
I take the point made by W200 that it was his professional duty to make clients aware of all the grants, etc they might be eligible for. But Bannon was also gambling to some extent on his inside knowledge. It put the reproducibility of the house budgeting in question - and to some degree also the series' integrity.
The thing is that Bannon has always gone over budget by around 30% and he's never left a big enough margin for the nasty surprises like structural issues met during refurbishment. Daniel O'Donnell got his budget inflated by over 100%, though he could afford it. Quantity surveyors have despaired of him through the series and seem to spend most of their time pulling up his arithmetical trousers. I see their point of view in as much as they get no credit for shaving off loads of cost if the final bill still strains the house owner. If anything, the QS gets the baddie name as they're always saying no, while the architect is forever trying to open up more space and light - at whatever cost - and is cast as a visionary.
Bannon isn't the worst of those who managed to get a regular gig off RTE despite their pedestrian abilities. Look at Hugh Wallace for Chrissakes - he is paid for basically squirming on about balmy interiors.