Hi Johno, You seem to have picked a Lulu as a project here. This reinforces my belief - that the further you go back in history - the more difficult it gets to find the details you may need. But don't let that stop you - makes it the more fun to chase down - and you will get help from some of the REAL experts in these areas - as you have seen.
Her's a couple of pics I copied from Wikipedia - just to help generally. They don't show Scots Guards - because I don't think they were at any of Marlborough's famous battles - they were busy in Scotland at the time you are interested in (c.1704-9).
First one is of Duke of Marlborough signing despatches in 1704 at Blenheim-Bavaria in 1704. This will give you an idea of general uniform appearance then:
Second one is of Battle of Blenheim itself. Note the fallen drummer at the left - and the size of the drums - which were generally much bigger then - than now.
Both of these pictures are in the public domain - according to Wiki - so are okay to reproduce for private study, incidentally. The tapestries at Blenheim Palace are also good sources of uniform information too - so you could have a look for pics of those too.
My last suggestion, is try and get a look at a book called "British Military Uniforms - from Contemporary Pictures from henry VII to the Present day (1957) by W Y Carman. It has some excellent pictures of Scots soldiers around thae time you are interested in - and good text descriptions too. (I picked up a copy from Amazon for around £3.[GB pounds]).
Anyway - hope this helps - don't get put off by difficulties - it may take some time - but with perseverance - you'll get there, I'm sure. And you are not being "too picky" - I'm like it too! Best of luck johnnybach