The UK did have an (undeployed) launch capability into the 1970s. There's a history of the US making allies prove they can achieve some capability, then selling

The UK did have an (undeployed) launch capability into the 1970s. There's a history of the US making allies prove they can achieve some capability, then selling them the same capability at lower cost. US concerns at the small size of the UK polaris force probably factored into the sale of Trident missiles (which allow many more mirvs).