The UK had nothing to do with any of the nuclear arms reduction treaties. START, SALT etc are signed between the US and Russia.
House of Commons Hansard Written Answers for 13 Dec 1995 (pt 19)
'WE177 Free-fall Bomb
Mr. Foulkes: To ask the Secretary of State for Defence what consideration led to the decision to withdraw the WE.177 in 1998; what was the original date for withdrawal; and on what date that decision was taken. [5165]
Mr. Arbuthnot: The decision to withdraw WE177 from service by the end of 1998, announced on 4 April 1995, Official Report, column 1097, was reached in the light of the good progress being made in providing Trident with a sub-strategic capability. This capability will be fully robust when Vigilant enters service in 1998 and there is no requirement for us to maintain two systems in the sub-strategic role after that point. We had previously assessed that WE177 had the potential to remain in service until the early years of the next century.'
See SALT and other links to START/SORT
Strategic Arms Limitation Talks - Wikipedia, the free encyclopedia
TJ