This is an idea from the USA that would work well in the UK and Northamptonshire especially. An ADU can be used to house a parent, a child, be used as a home office, holiday cottage etc. The important aspect is they remain on the original plot, are not separated off and remain in the same ownership.
They increase densities without using up agricultural land, use the existing infrastructure, and can provide additional income to offset increasing living costs. We could easily develop a similar strategy here if we choose to. Any prospective clients, or local authorities, or contractors interested in investigating the possibilities with my practice and experience with the Association of Self Build Architects (ASBA). They could be 'traditionally' built, timber-framed, modular, or use SIPs (structurally insulated panels). There are a few planning restrictions but common sense may prevail if presented correctly.
The borough of Kettering is full of such opportunities and will help to overcome the housing shortage. Currently redundant farm buildings and town centre upper floors are another opportunity where my skills as an architect could make you money.