Well I have installed the new tubes and am quite pleased. After a couple extended listening sessions have concluded that the upper mids and treble are more refined and the imageing has improved.
Just for the education, after I have gotten more familiar with the new sound my plan is to reinstall the original tubes to get a better handle on the differences. After which, I have no doubt the Mullards will remain.
Jeenam, I considered the Gold Lions. May try a set of these one day
Thanks to all!