A fellow TMer messaged me to remind me that the belt can be removed by loosening the adjuster bolt on the slotted arm and moving the alternator down to slacken the belt. This I had already tried but the alternator would not move enough to allow the belt to come off the pulleys, but it did trigger a thought about size of belts and were they the same. I looped the new belt over the top pulleys and realized it was lightly larger in length than the one fitted, so loosened the adjuster bolt moved the alternator to slacken the belt then cut the belt to remove fitted the new belt and hey presto all is good.
