This could also be coloured by my soft spot for the BAC 1-11 (which I thought was a lovely design and built like it was hewn from granite but let down by the choice of engine).
At the time the only engine available for the 1-11 was the spey as due to exchange regulations. It was not possible to purchase non UK engines.
An attempt to re engine with the Tay later on did not come to fruition.