Waiting for the AW681 to be developed was the reason that the HP Hastings remained in service as long as it did. As soon as the axe fell on the 681 so negotiations began to replace the Hastings fleet with the Lockheed C-130 began. HMG wanted to cram in as many UK systems into it as possible, thus driving down the US$ costs and generating more UK jobs. They began with wanting to replace the Allison T56's with RR Tyne turboprops. That was politely declined but, by shoehorning in copious UK navigation electronics as well as an autopilot (that took one look at the US looming and went into an immediate sulk), PM Harold Wilson was able to declare to the HoC that half the cost of the 60 strong fleet was in pounds Sterling. Rustling of order papers, prolonged rustling of order papers, etc, etc....
By 1968 most of the Hastings fleet had been distributed to various RAF airfields for fire practice, as the Hercules C Mk1's flew in to replace them.