It all comes down to a collective agreement,in other words you have instructed the union to act on your behalf.
Bearing in mind RM are clever at distorting information,i.e. colleague shares,that are not actually shares,but profit
related pay.
yes,they have to give you reasonable notice of any change,but this has seemingly been done through the union,and/or
on a notice board.
but the fact is your contractual hours have not changed,it is simply your shift time that has altered,as RM say this is
down to new legislation,and in the best interests of the business(delivery best practice)i fear the union can only appeal
to RM's better nature.
The standard letter that Postman has added would be intended for those that oppose the later starts not for those that
are unable,there is a subtle difference.
Your employer should offer you an alternative,however i'd be prepared to fight your own corner because i don't
sense much support from the union.