Which begs the question - do Scottish notes have fewer or less effective anti-counterfeit features and are therefore easier to forge? Or is it more to do with being less familiar to most checkout assistants in England and therefore less likely to be caught?
Scottish notes are generally significantly more advanced than their English counterparts. In the late '80s, the current series of RBS notes entered circulation, featuring (for its time) advanced security features. They featured UV ink which, whilst commonplace today, was not used by the bank of England until almost a decade later. These notes remain in circulation today. Our higher value notes have also used colour shifting ink for longer (which I understand is almost impossible to counterfeit), metallic inks, "see through" features (that require the note to be printed perfectly), and various more advanced holograms.
The new English £20 notes, and particularly the new £50 note, are fantastic and easy to check, particularly compared to the older ones (the old £50 notes featuring Sir John Houblon were really poor).
I have a £10 note in my pocket which features a patterned security strip (which is harder to forge than an English tenner), three types of watermark (vs 1), a depth image hologram (vs a normal hologram), and a "hidden" number that can only be seen when the note is tilted (not on the English notes). Having said that, in general, the key security features are the same on Scottish and English notes, and I don't really accept that you need any special training to be able to look at a watermark and security thread, and feel for raised printing.
In my experience, we got more counterfeit English notes up here than Scottish notes. This relates well to statistics I saw once that even in England, you're more likely to come across counterfeit English notes than Scottish ones. What alarmed me with the English fake notes was that they were generally much better quality than the Scottish fake ones, which is probably because mass manufacture of counterfeit banknotes is more profitable for notes which are more widely accepted. One English £20 note (one of the new ones with Adam Smith on the reverse) was very well manufactured - I suspect a lot of retailers would have taken it. By comparison, Scottish fakes tend to be very poor quality and quite easy to tell apart from genuine notes (although that's easy for me to say, handling thousands of them every day).
By the way - don't rely on counterfeit detector pens. In any currency. They're hopeless, and have high false positive and false negative rates. In fact, I'd actively encourage people
not to use them because it makes you rely on just one security feature when there are multiple on every banknote, and indeed it is very easy to foil such a pen. They are iodine pens detect starch in paper, which is absent in genuine banknotes. However, starch free paper is relatively easy to come by.
I've already posted a link somewhere above to the Association of Scottish Clearing Banks Website that shows the various features on the different notes, and is a useful resource for any cash handler who would like to learn more.
. 
