Sorry chaps for my lack of knowledge on individual names of parts but in the picture above. The part in the top right hand corner was the offending item. I basically had the arm located incorrectly into this part hence lack of throw on the plunger.
Silly mistake but one I’ve certainly learnt from!!
Ben, many thanks for sharing your experience here. I'm sure in the future, it will help others.
A close friend once said to me 'There are no mistakes, just learning experiences'. While at times, these 'learning experiences' can be frustrating, if you stick at them and beat them, there is volumes more to be learnt from that than just opening a box and having it play jingle bells.