Hi, in reference to one of the original questions, I have checked the index of this excellent Osprey book and re-scanned it contents: while they did see service with the English crown in Ireland, I did not see any reference to Gallowglass service on Continental Europe.
It could be due to geography, or the strength /weakness of regional relationships, or simply could be that Tudor armies already had heavy infantry whereas Irish Kern provided a specialised unit type that augmented Tudor army capabilities.
But in any case, I dont think it would be a huge stretch of the imagination to have
Gallóglaigh present in your campaign. Have fun
