No one really checks; they can come via Lahore and then go to GB.
No this is a completely separate region with different ethnicity, languages, cultures, traditions and histories. Modern-day region of Gilgit Baltistan was invaded by the Sikh Empire and later forcefully annexed by the Dogra Dynasty. A brutal genocide against the locals ensued. One rupee was given to anyone who brought the head of a Muslim man to the Maharaja. One of the worst massacres also occurred in which 2000 Yasin Villagers were killed and or burnt alive.
They always resented Dogra rule and in beginning in around 1940's they began to launch revolts again and a long insurgency ensued. In 1946-1947 Baltic soldiers serving under the Dogra and British rule mutinied, recaptured their region (aided by Pashtun tribes) , declared independence and opted to join Pakistan.