mrkfm - there are virtually as many theories about what caused past recessions as there are economists trying to make their mark, so yes, such discussions will run and run and there will never be agreement.
However, as someone whose approach to economics is very simple - based on the question "can I afford it?" - I would say that the balance of payments indicates there was only one recession in the late 80s.
No doubt there were multiple influences on the balance of payments following that stock-market crash, but it is true to say that the UK economy came back into balance within a few years under the Conservative government.
However, the economy immediately went into a controlled nosedive under the stewardship of Gordon the Moron. That decline was predominantly a result of UK government policies, and only affected slightly by outside influences. The economy was in a consistent year-on-year decline (as indicated by the current account balance) until the Coalition took over.