"Perhaps divest ourselves of the Northern Ireland too. It seems to cost us billions."
Not so easy. It takes two to tango!
As per the good Friday agreement a referendum for reunification can only occur should the Secretary of State consider that at any time it appears likely to him that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland."

This of course assumes the Irish Republic should wish to accept such a potential liability and passes the required legislation to allow for a successful outcome.
"THe relationship should have been mutually beneficial, and would have been if Britain had opted for c-operation rather than the tanks and the Paras"

Well that has to be a unique interpretation for explaining the troubles. Realistically it will gain zero support from serious historians.