Luggage Dimensions Query


Hi, looking at heading on the European pioneer (May 22nd) and have noted the luggage dimensions.

I’m a kiwi heading to Ireland for a semester abroad before I head on my topdeck tour in May. Accordingly, my suitcase dimensions happen to exceed the required dimensions as it is such a long term trip but I am hoping not to have to purchase a brand new bag on my arrival to London for the Topdeck tour. Have read on a number of forums that dimensions aren’t usually checked and as long as it’s under the 20kg it’s fine, it’s a full trip so if somebody could confirm or further advise that would be great!