Thanks Mathepac.
They reverted today to say that in fact - my pension % is not in fact 4.5%, rather it is a set EUR amount which works out at 4.5% (effective ceiling cap on their contributions). So the pension amount I thought I was entitled to in my first post is even less as their admittedly-correct pension number is based on my starting salary, and not my increased salary.
But as the 'clause creates moral difficulties' to HR now, they will increase my pension entitlement to 4.5% without cap.
On their side, this means - if my original salary is EUR'X', 10% salary increase for 15 months (effective 12.5%) by 4.5% (i.e. from 0% contribution as in excess of cap to 4.5%) = about 0.055% of my original salary will be added to their pension contribution for me in the next payroll-run.
I am trying not to write this in BLOCK CAPITALS as I feel so strong about this - but I am tempted to tell them 'no, I don't want it - I'm entitled to the larger amount/%, I accept you don't want to pay that and I can't force that - but I won't accept this'.
Can I ? Should I ?