Thanks for the input and assistance guys, but I've checked everywhere I can on the HOE website and as far as I can see I will not be able to have my new kilt and my wife's sash matching in Drummond of Perth Modern.
The heavyweight Drummond of Perth is listed as HW1678 Modern, while MW1210 Muted is given for the mediumweight sash material. Modern and Muted tartans are far different from what I can see.
If we cannot have the items to match, which is not surely an unusual request, we'll need to think about a different Drummond tartan which does, which rules out HOE.

So, the order for two jackets and waistcoats, (PC and Crail) one kilt with flashes and a sash will likely be going elsewhere, just because HOE cannot clarify the stuation or take an order over the phone when their webpage is so vague.
I've emailed them again tonight, but truth be told, I reckon I'll not be much further forward by this time tomorrow.
Is it just the tartan I chose, or has any other tartan presented such a difficulty?