Thanks for the welcome roadkill, and thanks for the heads-up bstrump .... I have, indeed, been trawling ebay and vast stretches of the rest of the internet, but to no avail, as yet.
Did however managed to locate an AMT 1/72 XB-70.
Am continuing the quest, and if push comes to shove will have to opt for the airfix kit, but i'd seriously prefer the monogram kit, if at all possible.
Failing success on that approach, I might even go for the 1/48 revell kit available at a shop just up the road .... but I find myself wondering "where will i put it?"