No sarcasm at-all DHU, but you are quite right about the fact that a newly qualified IRR holder, whilst permitted to flying long IFR trips outside class A, will need some significant further experience, and ideally a bit of mentoring before using it that way.
But I managed to fly Cranfield to Prestwick and back a few months after first getting the qualification, IMC most of the way, and IFR all the way. I was exhausted after, but did so safely and perfectly legally.
Any such trips do want planning as such, and the instrument flying skills need keeping current. Don't do it on the hoof. Many pilots have proved that you don't need a full IR to do so however.
G