Just a bit of an update just in case anyone else has a similar issue. The relay finally died today, which is a little easier to diagnose than an intermittent problem!!! The relay came apart fairly easily and a dry joint was found on the board (as suggested in other threads). Fixed this and the car started straight away!!!
Not only has this saved a lot of $$$ but there are only a couple of 2.5 16v Cossies here in South Africa and getting spares could have been difficult!!!
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