We know the number it impacts is 1.8 million so work from that. Roughly 30 million households in the UK.
There are roughly 28-29 million household in the UK and the 1.8 million are homeowners whose fixed deals will come to an end in 2023. In addition there are all the BTL mortgages where the tenants will be affected when the landlords have to pay more. While not a high proportion overall 100% of those on standard rate and tracker mortgages will also be affected.
In the UK there are around 11 million mortgages and the 1.8 million comes from around 6.8 million of those. Pro rata 2.9 million mortgages will be impacted (directly or indirectly), 10% of households.